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Un des symboles suivants apparaitra sur la dernidre image de cheque microfiche, selon le cas: le symbole — ►signifie "A SUIVRE", le symbole V signifie "FIN". Maps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, planches, tableaux, etc., peuvent dtre filmds d des taux de reduction diffdrents. Lorsque le document est trop grand pour dtre reproduit en un seul clich6, il est filmd .4 partir de Tangle sup6rieur gauche, de gauche d droite, et de haut en bas, en prenant le nombre d'images ndcessaire. Les diagrammes suivants illustrent la mdthode. 1 2 3 1 2 3 4 5 6 THE GEOLOGICAL HISTORY OF SERPENTINES INOLUDINa SinDIES OP PRE-CAMBRIAN ROCKS, BT THOMAS STKRRY HUNT, M.A., LL.D,, F.R.S. FROM THK TRANSACTIONS OF THE ROYAL SOCIETY OF CANADA. VOLUME I., SECTION IV., 1888. MONTREAL: DAWSON BROTHERS, PUBLISHERS, isas I ^" ' -I Y— -^.— «^-»^«CTETr^- > ..i;., ni„„..«»..«i-n*AmArjitmUSKjr.'? 'rhBDrftO- r * 1 I i ] mm i m il i —iiwiiiir^aiiiiwii— ly A, S'SZ.A'l r 11 THE GEOLOGICAL HISTORY OK SERPENTINES INCLUDINO STUDIKS OF PRE-CAMBRIAN ROCKS, ■| I BY THOMAS STKRUY HUNT, M.A., LL.D,, F.R.S, KUOM THE TRANSACTIONS OF THE ROYAL SOCIETY OF CANADA. VOLUME I., SECTION IV., 1H83. ^ MONTHKAli: DAWSON BU0TJI1-]|{S, rUBLFSlIEKS, « Section IV., 1883. [ 16S ] Trans. Eoy. Soc Canam. X. — The Geological Ilistori/ of Serpentines, indmllng Notes on pre-Cambriau Rocks. By TiiO-MAs Sterry Hunt, M.A., LL.D. (Cantab.), F.R.S. (Presontod May 23, 1883.) l.—IIutorirnl /)i(ror/iwntinas and related rocks. Views of some Italian geologists. SerixmtineB at the geological congress of Bologna. IV.— /^ocA-s (if thr Aljii' iiDil the Apmnmn.—VAnW views. Studies of ( lastaldi, von I lauer and others. Ancient gneiss ; pietre verdi or greenstones ; newer gneiss ; youngest crystalline schists. Four pre-Candirian groups in the Alps detimMl. Rocks of the Apennines and the adjacent islands. v.— //((?i((» Sirpe»tiii,i>.—'\:hMr classification ; plutonic and hydroplutouiu thoories of their origin. Seriwntines of TuBcauy, Lignria and the Ali)s. Antiqiuty of the so-eallod tertiary sorixuitines. VI._7'7„i f/,, ),»(.« f,/.SVr/)«)i(/»(,».— Theories of plutonic and nei>tnnian uietasomatisni ; diagenesis. The derivation of si^ixnitine from olivine*, anxisting and, it is hoped, prepare the way for their reconciliation. Thest^ ditlerences nujy be considered under two heads : namely, the geognosy of serpentine, or its relation to the other rocks of the earth's crust, and the geogeny, or the origin and mode of formation of serpentine. Setting aside for the moment the question of the occurreu'-e of serpentine as an acci- dental mineral disseminated iiv calcareous rocks, and «'onsidering only its occurrence in rock-masses, either purt> or mingled with other silicates, the first quest ion which presents itself is whether such massive serpentines are contemporaneous with the eni'losing rocks, or whether they liave been subse((uently intruded among these :— iu other words, whether serpentines are indigenous or exotic rocks. tfZ)5?.S |IHWH MH *» l ^ ' -J>aWEI>^* ^QQ m. THOMAS STEERY HUNT ON THE S 2 Wo find at the beginning of our oeuiury, that the most competent observers were acrreod in ro-ardin? serpentines as stratified contemporaneous deposits in the so-called ;ilr; rocks, r^trin described those of Mont l^ose and of ihe ff^^^^I^^ tratific'd with .-alcareons and micaceous schists, ^vhilc Saussure lound those oi Mont Cer ■h to present similar condUu>ns, and described certain serpentines, found near Gc. oa ^ a terna ing with bands of calcareous, quartzose, and micaceous schists or argiUites. Humboldt: in like manner, noticed the stratified character of the serpentines near Beyru h ad .TameJon found tho.e of Rothsny. in Scotland, to be interstratified with micaceous and Lose schists, andwit' ■rystalline limestone, in repeated alternations, of which he gives a diac^ram, mentioninu-, however, as an opinion held by some, tbat the masses both of s r- peiUine Lnd of limestone " form great veins rather tban vertical sheets. -^;;-^;- describes serpentine as a primitive stratified roek, eonteiup.mnieous, nnd alteinatmg with '''''tTl^M.r we find, in 1S26, Maculloch. m his C.o^.,ir., n.sl,r.Hon ^ Eor^, sepa atiuo- the primitive rocks into two groups, stratified and unstratified, the latter con- i t nl of%-ran te and serpentine, He assigned as a reason for plaem. serpentine in th t e ^chL that it docs not appear to be decidedly stratified, but, at the same time, remark ^unlike other unstratified rocks, as granite or trap, he had not found -P-j^;'-^ U-t ramiMng veins. Subseciuent studies in the Sh.. land ^^-^^^^^^:^;^ L calls "an-importaiit corre..tion" in its history. >n the Appendix ^ ^j - -^ ^ u.med where he announces his (.mclusion that the ..erpentmes ■ -e stratilied lo. ks UKc Z^s'oTm ^' hLts, addin. a revised tabular view, in wlu-h they are included wiUi SJ'^trslratified division of the primitive rocks, granite .lone being retained m the unstratified division.! , ,, ,• r r'.v,„,-.,ll m^ M. Boase,inhis Prn.n; Orolo,,, in IHM, describes the seiT^-tin.s of ( o ii ^ as associated with talcose and chloritie and aetinolite-schists, and what had been .alkd assoaauu ^ ^ ,,,pentine seemed in some instan.-es subordinated. He ^:;™ : l:^:!:JtioJ ^a modes of oe,.urrenees with those described by M :^1 M -Be la Eeehe. in like manner, m his Geo,.,, of Con.r.U „.l D.ro. not., the se nn.^ passage of the seiTOi^^ into the hornblende-sla.e in many places, bu also i^s :;;;::::St ' hi^ision amid 'u. latter with fone ; ' a seeming contradietion which ho recog- ni'/es ])ut endeavors to explain.^ _ , I r Unlike Maeeulloch and Boase. Dela Beehe regarded serpentine as an eruptive rock of posterior ori-nn to the assoeiated schists, agreeing in lliis with Bronaniar^ who had ;! j:d ::"entine among plutonic rocks. A similar view was held by Elie de Beaumont || and by Savi. and, without entering into further details, we may iiotiee tbat they have been followed bv Sismondi. Lory, and others, who maintain the plutonic om-in ol the Alpine «^Uitine;. while, on the other hand, Scipion Gras, Gastaldi, Fa vre and Stapff regard them . Sec for tho toxt of tl.o above rofc-onn. .,,0 ,n„ta.ions in rinkeHonV r.tralo,n-, 1821, 1. 334-343 ; 11. 608:612. + IMaoulloch, Inc. cit., pp. 7S, 243, ()52-(155. X r.nafiO, loo. rit., p. 40. I ^;;; ^::;;::!;: t !j;;.sn,:r;vi,h VM. a. noan,n„nt ^ is.., , ..,..,1 l,is',.nnn.nt .onoa.uo do Scnarniont lu,,! loa hhu to rojort, as wholly nntonablo, tho thoory of their ,,lutoni.' ongu.. \ GEOLOGICAL HISTORY OF SEIU'ENTINES. 167 as of aqueous aud sedimentary origin. The views of the present s.hool of Italian geolo- gists, as well as Dieulol'ait and Lotti, will be noticed in part VL j t. In the United States, we hnd Edward llitchcoLk, in 1841, reviewing the opinions of MaceuUoch, Brongniart, De la 13eehe and others, and deciding that the serpentines of Massachusetts are to be regarded as stratilied rocks* Emmons, in 1842, after noticing the conclusions of Hitchcock as to serpentine, regarded it, nevertheless, as an unstratilied rock, but distinguish it from trappean rocks, inasmuch as, according to him, it is never found in injected veins or dykes.f Later, however, in 1855, he separated it from so-called pyroplastic rocks, like " basalt, trap and greenstone," aud included it in both divisions of his pyrocrystalline class : that is to say, (1) as laminated serpentine with gneiss, micaceous talcose and hornbleudic slates and limestone, and (2) as massive serpentine, with granite^ syenite, etc.J § 7. J. U. Whitney, in ls.31, included hornblende and serpentine rocks, together with magnetic aud specular oxyds or iron, under the title of '• Igneous," and the sub-title of "Trappean aud Volcanic liocks."^ Henry 1). Kogers, iu 1858, described the steatite belt on the tichuylkill Kiver, in rennsylvania, as formed from the mica-schists of the re-ion through impregnation from "the dyke of serpentine which everywhere adjoins it," Thus implying the posterior origin and eruptive character of the latter. Elsewhere he describes the crystalline rocks of the same region as including " true injected serpentines." He, however, looked on veins of quartz and epidote, and oven of carbonate of lime, as also of eruptive origiu.|| Lieber, at the same time, ill his report on the g.-ology of South Caro- lina, regarded not only the serpentines of that region, but the associated steaiite and actinolite-rocks as eruptive. § 8. In opposition to these plutonie views, the geological survey of Canada from an early date (1848,) insisted upon the stratilied character of the serpentines found in .he northern extension of the Green Mountain range in eastern Canada. They were shown to be accompanied by hornbleudic, steatitic, dioritie and other schistose rocks, as well as by dolomites and magnesites. The writer, iu discussing the relations of these in 1803, anuouiucd "the conclusion that the whole series of rocks . . . from diorites, diallages, and serpentines to talcs, chlorites and epidosites, have been formed under similar conditions," and were aqueous deposits.^] S^ U. Here, it will be seen that we approach the second question mentioned in § 1, namely that of the origin and mode of formation of serpentines, which, in the view of those who maintain its indigciiuus character, is, of course, closely connected with the prob- lem of the origin of Us associated crystalline rocks. The notions of the earlier geologists with regard tc this latter problem were, in most cases, very vague, some of them holding the view still taught in our own day by Hebert, that these rocks, including gneisses, * Goolugy orMiissiifluisott:, If., (illi. t (.(oology of Now York. Aorllioin Di.'iti-iLl, jip. 07-70, pp. 15-19. t Aiiiorifiili (ii'Dldgy, 1„ 4M, 'i (ioolugy of l.ako sjiii)orior, II., 'J. II Goology of Poiuisylvauia, vol. I. i.ii.ssiiu. Soo also tho aiUlior, L'lid ttool. Sun-oy of I'oim., Azoio Kocks, H Goology of Canada, i-. OK". Soo al«o tho autlior's CoulribiUioa.s to tlio History of Oi)hiolito.s, 1858 Amor Jour. Sci. XXV. l'17-L'2ti, and xxvi. ii:!4-'.'40. I ^gg TIT!. THOMAS STURRY HUNT ON THE "„ h cl .U."n u „V,- .onm.i.m^ ..f l,.n„,.ra„.r,. n ..1,1<.. .l...s..,.l .1,.. ,..;.-..« nn,-, an and substitution (we/fW)m(//(M/.s). ;„i .. Inns found nn ,S 10. Th. latt.v do..tvino. ^vhi.■h. in th. hands of somo o Us dis-nh's. oun - ..tonsion lhnU.d only l>y th.iv nna.inations, .vns at on.v npphod to -l'^-' ' ^ . s.,,>.ntin.. Sni..at.d vo.ks. d.stitut. of n.^nesia. and -avhonai.d vo..ks <^^>^^ ^^'^ .ould alike, it was n.aintainod, bo ..onvovt.d in s..vp.nt,n., .^.n-h .^^ ^^"^J^^ Z last term in the motasomatic .-hang.s of a vast numb.-v of uinn.al ^1^ !-' / "^ o lono-or no.vssary to suppose the dire.t deposition of a nia..u-stan sedunent. o, an n u tonXV".K.ms mao-neliau vo.k to explain the pres.n-e of .ontemporan.ous o^ o :!d :> P^ ti^es. Ti;e le,itimat.. out-o^neof this hypothesis is l.und in the teaeW^ Z^, n \s.S. (when h. et held the eruptive natur. of s..pentn.e, ^^^^^^ wi h o hev "trappean ro,ks.") that -'arauitie and trappeau mks' may in eeitain cases, ^ ' : ' d 1 ima.nesian sllieate, whi.h may be serpentine. taV. ehlonb> - ^P^^ ;^^^. ^ 1^ I have elsewhere shown howDelesse three yearslaier abandoned ^^^^J^'^ somatie hypothesis and the notion of the eruptive ori.iu of the ^^-^^'^ , / ' ^^^ l" view whieh I had put forth in 18.. and IS.lu, that the serpentnu. we e undouU ^ ;:c^.enous ro.ks, resultn., from the .dteration ^^ f'^^^^^ZtX^^rJi tho' same time as a rone.ssion to those who maintained the oerurr.n.v ol eniptiu s.ipui • eH^^'said that -the tinal result -f heat aided by water on silieated ro^ w^iid,: their sottenin., and, in .vrtain .ases, their extravasation as Pl-Joiu-oeks . V 1 1 .. " \u Mil ("isos altered and displa.vd sediments. sS It (n-alo"i»al and litholoi>-i>al characters. || ,, , t i.,-1 ;» l«r,n hi. An,., ,.a,.,.|ul s,n,li,.-,. alik,. in .1,,. IM,! a„.l in ,h,. l.i„.ra.o,y, T ---Mm ..0 ton,ai„,a,n .hai iho ori..i„ of .,.,,-". "'^ ■■'■'-'■\-''f ';::;;■!. J ^ramn ts": deposits of hydrous sili.-ates, like the magnesian marls oi the 1 aii.s l)a,sin, aim in r^ V nl Delesse teaehin. this doctrine of the origin of these rocks from the altcrat on ::l::!aiIrmetaniorphismof suC magn-sian precipitates, but dc^-l^mihe^s^ ~^yM^Z^^ ;..:;,^^unrnn. ,.... i..,....,i„.. .. ,.,is vU.., .,„ a,U„o..V .■iK.n.i.a, an.l Cicologiral Essay.s, p, 2i>4. t ChMiiifal and Goologiial Kssayn, p. '.>il. t Ann.. los Minos (.')) xii. ,500, ami xiii. :;!i;!, 41."). % Cliciii. un.KiiMil. KsaavM, pp. :!lii-;il.s. II Anicr. .lour. S(i.,xix,, ;;70. GEOLOGICAL HISTORY OF SERPENT INKS. 169 my toachin-, as above, that " the plutomc rork, are formed from the metamoriMc rocks, and repremit Ih- maximum of i„l,;wl,„ or the extreme term of or,>eml mrtnmorphismr * The history ol the aba.Klonmo.it ])y D.'lesse of his Ibrmer view of the pl.ito.iie for that of the uep- tu.iiaii origin of serpentines, and his arceptance at the same time of the liypothosis of au aqiieous ori-.n of i-lutoni.. m-ks, is signifi.ant as a recognition of the new ideas for which 1 had eonto.ided, u.id whi.h eo.istitute a new departure in theoretical -eogeny. § 1:3. In further ..xpla.iation of this sour.e „f ma-nesia.i silicates, i" was shown by the writer in a seri^^s of experi.n...its, the results of which were published in IS.Jo that whenever the comparatively soluble silicates of alkalies or of lime (which are set free by the decay of crystalline sili,.ates, and are found in m nv natural waters), are brouo-ht in contact with solut.o.is like sea-water holding magnesian sulphate or .hlorid double de- composition takes pla. e with the separation of a very insoluble g,.latinous silicate of mao- uesia ; and further, that pre.'initated silicate of lime is decomposed by digestio.i with suci raagues.a.i solutions, its lime becoming partially or whollv replaced by ma"ncsia This process, it was pointed out, is the reverse of that which happens when car- bonates ot alkah.'s or of magnesia come in contact with sea-water, in which case the com- parative insolubility of carbonat., of lim.. .auses the dcomposition of the soluble ."ibMum- salts present. '• In the one case, the lime is separated as carbonate, th.. magnesia ivmaiuino- in solution ; while in the othe,-. by the action of silicate of soda (or of lime) 'he ma-nesia IS remoyed and the li.ne remaius. Hence carbonate of lime and silicates of magnes'ia are ioundal)u.ida..tly .n .lature, Avhile ••arbouate of magnesia and sili.Mtes of line are pro- duced only u.uh>r local and exceptional conditions. It is evident that th.^ productio.i from the waters of the early seas of beds of s;>piolite, talc, serpentine, and other rocks in which a magnes.an silicate a1>ounds. must, in clo.sed basins, have given rise to waters in which chlond ol .alcium would predominate.- t Thegenerationof magnesian silicates in aqueous sediments was thus shown to be the result of a natural process as simple as that ...ivino- rise to carbonate of lime. ° '' § 14. There are many questions coniuvted with this theory of the source of serpentine and related rocks, such as the ])robable variations in the .•o.niK.sition of (he orio-iual sili- cates . the.r a.lm.xtu.v with other sili.ates and orrbonates ; the ..hanges wrcught'in these by subsequent chemical reactions, resulting in the genesis of talc, serpentine, e.istatite and olivine, and, ..i certain cases, the subsequ.Mit .•ha.,ges of these anhydrous snocies • the prese.icem these .uao-nesia.i mi.ierab of ferrous silicate, whi.'h is so abundant in many se,-pe.itiue.s, and its relations to the as yet ob.sctre problem of (he o.-i^iu of ghmconite. Itself .some .mes a more or less .nag.iesia.i silicate ; iinally, the notable iact of the presence 1,1 most of these mao,iesian rocks of small portions of rarer metals, su.>h as nickel tuI .hrom.um, ^vhi.h is to be .-onsidered in connection with the similar nietalli.- iinpreo-na- l.on ot certain mineral waters that may well have i,i(ervene,l in ,hc production of these magnesian silicates, .\11 of these are important points, which must be reserved for fudire discussion. j 15. One grea( object i„ geology is to discover by what natural processes the different * DtOcsso, KtndcH .snr Ic, ^Sn-tainoriilii.smo, IKiil, p. 87. t Anicr. Jour. 8d. (l>) xl., 10 ; al.so Cho,,,. ami Gool. E.ssays, p. VTi. Soc. IV., 1S83. 22 \\ -170 DE. THOMAS STEBEY HUNT OX THE homioal olomonts have boon .sogreiraiod and oombinod during succossivo ages in the forms iu whi.h wo ncnv lind thonr in the earth's ernst : in other words how, ironr a onec.hoaio- .eneons nrass have been separated quartz, corundum, bauxite, carbonates ot < aUnum and mac.nosium,as well as carbonates, oxyds and sulphids oC nranganese, iron, zurc, copper and otlier motals. Not h-ss important is the problem of the genesis of the corre^ londing pro- toxyd-silicates, and especially of those of <.dcium, -'-^-^ , r'^'^^^";,^^;:^ form often ^vith little or no admixture, considerable masses ui the earth s eiust. Ot th. sc it ,s unncessarv to say the magnesian rocks under consideration constitute an important part and all anidogies lead to the conclusion that their constituent elements have been brought tog..therby a(iueous processes, such as we have already indicated. II,_SEl!in-:.\TINES IN N<1HTII Ameku'a. ^ W II is evident thai ii we once come to regard serpentine as a rock l^.rmed from a„ueous sediments of chemical oridn. there is no reason. . priori, why it may not be iound, lileli,nestone,d.>lomiteor.ypsuni. intercalated in st rat iiied deposits a ditlerent geolo- .ieal horizons, and with diili.rent lithnln.ical associations. Several such h.M-iz.ms ot ser- pentine have been observed in North A.ierica. which will be noti.ed m ascending order. Tn.luded in the ancient gneissic series to which the name of Laurentian has been o.iven serpentine is livciuently met with associated alike with beds of crysUdlme lime- stone and with dolomite. In these beds, the serpentine is often dissenunated m grams r ll.ni, " d like this sid;s,ance. sometimes attain large dimensions. These serpentines occasi.maly ;,,,lude ,be .al.areous skeletons of /;.:... ('ana>fn>sr, the silicate rep acng the so t parts ,Ue or..amsni. as described by Daw.on an.l Carpenter. < .ccas.ona ly. tie- serpentim-s ot t'h i;..u i;.rm beds.of considerable si.e, either pu. r mn.gied only w„ s.nall ,K>r- > of eal..ite or dolomite, Of ihese. many instances arc see. wnl. l.e l.nus.mcs ol th u entiau in Canada, and a reu.arkabl.exampl urs a, Xew IJocielle, on T.ng Island . strike, the u In.h. hcin^ .onloru.abb- n.lerstra- IhHl with massive .nei..esand black hornbLnd,,- roek^ wi,h red .arnet. * Ihe uvn- ,,,,.,1 ,,,,,,„,,,.,. of, lie serpcntiuo found with ,hel.a,uvn„an h.ncMone. have been else- ,.,,„,„ ,l,..,.ribed bv the proen, wri,er. Their lower ■^pe.ili- uravi.y. a,.d genevally paler ,..,1,„. ,o..v,her with a la,-er ppn-rt io,. of eond.in.-l water t serve. ,n .Mue eases a, least, to diMin-mish the serp...dines of this horizon front tle-e ,o be n.niioned as o.eurnn- .n „,„n,^,,„,i;ni series, To this mavb- ad.h.d. a Miiall-M' aniounl of combined iron-oxyd, , ;,ses ilie ;d.M.nceofconii.oundsof uulA ;,nd .hronie. whi.h aro almost mvari- an< ni nio> M.'nr in, a.r,mn,,.f ,l,is Inralily s.. Mntlna-, d.-.l. First Pistrirt ef New Ynrk i IMi; i. p. UU; aUo.I. D-Duim, vrr|«'iilim'-,,src (Iru!. Ciiiuiila lsii:l, pp. 171, V.il ; AiuiT. .inur. Sii. .'■'•' XX., ;;ii-:'.-. •I ipi|iin< ;niil nii.ilv ilUornlllliiilllinll,-, U) Ihe lli-lniy i.r<'| ni'v i.n ipl'i'ilitc.s I Is.'iSi, .\nier. .Iciir, Sri. i/J i x.\vi„ pp. l.';il-J3(l to in § H) which is now know)i to mark a dellnite geological horizon, the serpcuitines are found intorbedded. sometimes mingled with c'arbonato of lime or of magnesia, but seldom or never presenting varieties like the granular ophicalcite of the Laurentian. To this horizon belong the serpentines of eastern Canada, found in the conti- nuation of the Green Mountain range (llie alt.'red Quebe.' group of Logan), as Wi'll as those of Newport, Rhode Island, and apparently those of Cornwall. Anglesea and Ayrshire in Croat Britain. Tho serpentines of this series are darker coloured than the last, and gener- ally contain small portions of chrome and nickel in com])iiiaiion. * § 18. Serpentines are also met with in (Cistern North America in somewhat ditfereut associations from the two foregoino- groups, aiul apparently belonging to a tliird geological horizon. Tlie determination of tho precise stratigraphical relations of the serpentines in question presents, however, certain diliiculties arisino- from con.siderations Avlii.h will be made apparent in the sequel. Serpentine, thouiih not exemi)t from snbaerial decay, resists this lu'ocess bett(>r than hornblendic, Icldspathic and calcareous rocks. Hence it happens that in regions where tlicso are decomposed and disintegrated to considerable depths, asso- ciated masses of serpentine may be found rising our of the .soil, without any evidences of the lu'ocise nature of the rocks which once enclosed them. Illustrations of "this condition of things arc found in th(> vicinity of AV"estchester and of Media, in Cnioster county. Penn- sylvania. Tlie underlying rocks in (his region are known to l)echiollygnoiss.'S, with horn- blendic and mica-.scliists. and include what are believed to liolong to two distin.t series, botli of which are well displayed in the .section seen on tho Schuylkill K'iver. below Nor- ristowii. Here the older Laurentian gn.'iss, such aN it apiiears in the South M(mntain and the Welsli Moinitain. comes up in lUick Kidge, while tho newer gneis- and mica-schist series is soon siKveeding it to ilie southward, at Manayunk and Chostiuit Hill, at which latter hx'ality it also appears on the iu)rlhsid,. of the narrow Laurentian belt. In this section, as it is <'xi)oscd on the Sclniylkill. a holt of serpentine, with steatitic and chloritic rocks, appears between the two .s.'ri.'.s. but cLsewliero it is wanting ah)ng the outcrop of the older gneiss. In the loralities farther west in Chester county, already mentioned, at Westchester and Media, whore tli(> rocks adjacent to the sovpeutiiio are disinteniatod, and iiave disappeared, from decay, it cannot bo dotorniinod whet lier these serpentine-masses bolonu' to the older or tho newer serie.s— which latter appears to he similar to that including the seri>ontiuo and chrystilito rocks of Mitchell county. North Curoiiua. (j UH). *rnrHll lUVolllit of lllc.s,^s(M'|)Olltilli'N, stv (i.Mild^-y nC ( 'iillMdil, ISi;;!, i.p, -irj, iKlS-dlL' ; hImi Cenlrilmtieliste tiio llistdry (iroiiliidlilos (l.'^.IH), .Viuor. .loiir. .S'i. i^-J) xxv., l.'17-L'L'i;, ■ 172 DR. THOMAS STKRRY HUNT ON TIIK I § 19. The serpeutine of Brintou's quarry, near Westchester, Pennsylvania, is distinctly bedded, granular, and often finely laminated, with disseminated scales of a micaceous mineral, giving it a gneissoid structure and aspect. A black schistose hornblendic rock, with red garnet, is said to have been found in an excavation adjoining the serpentine, and fragments gathered in the vicinity showed thin iuterlaminations of black horn- blende with greenish serpentine. The dip of the strata, of which several hundred feet are here exposed, is to the northwest at a high angle, approaching the vertical. They are traversed, nearly at right angles, by a vertical granitic vein, which has been traced for many hundred feet in a northwest course. This vein, which is generally from three to six feet in breadth, is white in color, and in parts may be described as a fine-grained binary granite, the feldspar of which is superficially kaolinized. In other parts, it becomes very coarse-grained, presenting large cleavage-forms of orthoclase. A banded or zoned structure, parallel to the well-defined walls, is observed in some parts, and in one case a lenticular mass of white vitreous quartz occupies the centre. This vein-stone, which carries black tourmaline, and is said to have afforded beryl, has all the characters of the ordinary en- dogenous granitic veins found in the gneissic rocks of the Appalchians, which veins I have elsewhere described in detail. * § 20. The rocks in the vicinity of the serpentine near Westchester are, as already said, deeply decayed, but wherever seen in the cuttings arc found to be mica-schist and mica- ceous gneiss. Such rocks, with a northwest dip, appear to underlie, at no great distance, the mass of serpentine exposed at Stroud's mill. Similar rocks are also found on the rail- road between Westchester and Media, where they are exposed in a cutthig near the latter station, about a mile from which is found a great outcrop of distinctly stratified serpentine, resembling that of Brinton's quarry, and with a steep northwest dip. It includes an mter- stratified mass, about twenty feet thick, of a fine-grained reddish gneissoid rock, approach- ing leptynite or granulite in character, divided into distinct beds generally from four to eight inches in thickness, between which are sometimes found layers of a few inches, of a soft serpentine, and, in one case, of a broadly foliated green chloritic mineral. Consider- able differences in texture and aspect were observed between the serpentine-})eds below and those above this quartzo-feldspathic mass, which is indigenous, and not to be con- founded with the endogenous transversal mass described at Brinton's quarry. § 21. Serpentine-rocks also occur on Manhattan Island, in the city of New York, where"they are still exposed between Fifty-seventh and Sixtieth streets, west of Tenth avenue, and are directly interstraiilied in gneissic and micaceous rocks, which may either belong to tlie older gneiss series of the Highlands, or to a newer group. Associated with the massive serpentine of this locality n-c found small (inantities of a granular ophicalcite, and near it is a mass of anthopliyllite-roik. This locality was long since described by Dr. Gale, when the rocks were more i'uUy exposed than at present, t § 22. Serpentiue-masses are also found in t)ie vicinityof the last, onStaten Island um\ at Iloboken, in both of which lo>a'iitii>s the encasing gneisses, seen in New York city, are wanting, and the serpentine appears along the eastern margin of the triassic belt of the region, The serpentine of Staten Island is of much interest, as it presents many fea- * Amor. .lrders of the serpentine are spread horizontal cretaceous clays, partially overlaid by drift, while on the north side of the island, where the serpentine hills rise abruptly at a little distance from the shore, are the only known outcrops of other rocks ; one a ledge of anthophyl lite-rock like that accompanying the serpentine in New York city, and another, a few hundred feet distant from the latter, and from the serpentine, consisting of a coarse pegmatite, having all the aspect of an ordinary concretionary granitic vein, and containing besides crystals of orthoclase, sometimes twelve inches in length, small portions of a white triclinic feld- spar and rare crystals of red garnet. A second smaller outcrop of a similar kind is found near by. These granitic and anthophyllite-rocks appear from beneath the water and the sands of the beach. I 23. Such an ccrurrence of serpentine, rising from out of the nearly horizontal and low-lying mesozoic strata of the island, was well calculated to sustain the notion of the eruptive nature of this rock which was put forth by Mather in his description of this locality. He, m his report, above cited, included the serpentine in his "Ti-appean Division " in the same category with the adjacent diabase, regarding the serpentine " as due to the action of the same general causes, modified in a manner unknown to us." * The history of this area of serpentine becomcB intelligible when studied in the light of the facts already menti.med above. It was apparently, in triassic time, a range of hills left by the disintegration of the adjacent gneiss, the lower-lying surfoces of which are con- cealed beneath the newer sediments of the region. Since ihat time, as I have elsewhere pointed out, t the serpentine itself has undergone a process of subaerial change, as is evident by the layer of decayed matter, with included masses of limonite, which, in those portions that have c-scaped .-rosion, still covers the serpentine to the depth often or twelve feet For many of the above details of this region I have availed myself of a description ot Its geology, witli map and sections, pul)lis]ied in 18S0, l)y ]),•. N L Britton ± of the School of Mines, (.'olumbia College, New York, with whom I have lately had the advantage of visiting this interesting locality, and to whom I desire to make my grateful acknowledgments for valuable inlorination respecting it, § 24. The »,.rpentine-ro.k which is seen at Castle Hill, ITohoken, on the wo,st bank of the Hudson, opposite New York city, is believed by Dr. Britton to ],e a continuation of that oi Staten Island, und, like it, lies on the eastern border of the trias; while the * I/)C. cit., p. L'S;!. t Aiiu.r. .lour. Hcionoo, (I!) xxvi., L'tMi, t Tho Geology of Ru'lunond Co. (StaUm Island), N. Y., Ann. Now York Aomlomy of Soionces, Vol. II., No. 0. t > 174 DB. THOMAS STERRY HUNT ON THE \ I 1 1 serpentinfi-oiiccrop on the -west side of New York city has a strike which would cany it to the east of Staten Island, nnd probably con'osponds to a repetition of the same belt. Grneissic locks are met with in a boring near the serpentine at Iloboken, and are found in the small islands between Manhattan and Stuten Island, so that there can be no reason- able doubt that the serpentines of staten Island and of Iloboken belong, like that of New York city, to the gneissic series of the region. The determination of the precise relations of these giiessic rocks to those accompanying the serpentines of eastern Penn- sylvania, already described, remains for farther inquiry. § 2"). We have next to notice the occurrence, in Pennsylvania, of serpentine in the Lower Taconic rocks of Emmons, the Primal slates of Rogers, which he supposed to be- long to the horizon of the Potsdam of Ihe New York series. In ac(>ordance with this view, we find that in a report by Clenth on the mineralogy of Pennsylvania, in 18*75, the occur- rence of serpentine is mentioned, though without any details, in the " Potsdam sand- stone" near Bethlehem, at the iron-mines of Cornwall, and also in the township of Warwick, Chester county. * This statement is, however, misleading, inasmuch as the serpentine is not found in the sandstone-rock which has been conjectured to be the equi- valent of the New York Potsdam, but in certain schists and limestones, referred, rightly or wrongly, to the same geological horizon, the so-called Primal slates. § 26. I have had an opportunity of observing the occurrence of serpentine at Corn- wall, where it forms small irregular masses disseminated in a bod of crystalline limestone, itself subordinate to the groat mass of crystalline schists which include the magnetite largely mined at this locality. Serpentine, generally with limestone, is found at many other localities associated with iron-ores at tlic same geological horizon, as at Fritz's Island and elsewhere, near Reading, at Boyerstown, and at the Jones iron-mine, Jiear to Warwick, where it is foimd in small lenticular masses im])edded directly in the crystalline schists which, as at Cornwall, include the cupriferous magnetites of the region. These schists include hydrous micaceous minerals, among which are chlorite, and the geeenish foliated silicate of copper, magn(>siiim and aluminum, to which I have given the name of venerite. The manner in which lenticular masses of pure serpentine, sonn'times only a few ounces in weight, are found imixiddcd in these si'hists, not less than the mode of their occurrence in tL > limestones at this horizon, is such as to suggest very forcibly iho notion that they have been formed under conditions not unlike those which have given rise to chert or to iron-stone nodules. No large masses of serpentine have, so far as known, been found at this horizon, yet they may be expected. § 27. We have next to notice the existence of a bed of serpentine at Syracuse, New York, which was, in 1839, examined and described by Prof. Vanuxem,then engaged in the geological survey of the State. The locality, " on ihe Fort-street road to the east of Syracuse" or, according to Dr. Lt^wis Beck, "on the hill a short distance east of the mansion of Major Burn(>t, at Syracmse," has long since been concealed by the growth of the city, and we have, so tar as I am aware, no other description than those givc^n by Prof Vanuxem in 1839 and 1842, f of which, on acccnint of the intc ■ ■tt and signilicance of this curious *• SociiikI (i(Mil( lyrical Survey f,'y of tlio Third DistricI (if N'nw Ydik, pp. 200 and L'H3 ; riiml Hoiiort on tlio Goology of tlio Tliird Dl.striit, i^). 108 and 110, and Bock's ISlinoralogy of Now York, p. 27 OEOLOBICAL HISTOEY OF SBBPENTINKS. 178 occurrence of serpentine, I mate the following summary :-The rocks of the r ■ 0, I, well known, belong to the Onondaga salt-group of the New Tortt!) 1 *'°''' a position near the summit of the Silurial heinj overlaid 1 v til I ow H u"! "''""^ resting upon the Niagara division The straf, ,re ,. 1 I rT Holderberg, and undisturbed and nearly horizontal ' the inc n'tie' ,', , " "'"""''""t ""is region, being less than thirty feet to the li I b .u VT"' '"' '"""""'^ ^' ^"'"«™. Onondaga salt-group I silt to ^r . "'"^ ''"■*"™- ^''» '«*"=- »' ">« limit, it°is thinmX f wfr ;:r;°""rir'''' ^"''- ■"" '" ''^^ "--'-■ duis!„-'in hTforxitrubrmirr r d"; """r"; *' °*^'°"'"» ™"'-" o"'- marked by hopper-shap d ti e "ZmI f ",' 'f "'"'''" °' "■"""■ "'''i''' »« <•"«■ in,bedded crystals . f a-s X 1?! d k"" *,""=* *" '™°^-"'' ''^ -'"'i™. <>' .nite, generally drab or ;„ 'in I'^Th ,", i.i:: totis '°"'"' """""i" """"^ ''°'°- in most cases communicate with one a, oth r Th ^V"^ '""="'"■■ "' '°™' '"'1 .*erica> crusts, besides some pXr," :.rZ a ^r^ir'TZr rir T^" ever with thos: d:;;!: 'i,g ir:-::.'''!: "°'™' '""*; "r "° """'°'"'- -""• that parts of the rock are disneled > . . '" °"'' '°'-''''">'' ""«' <"="» *«' celK^an effect U it" ^riw^^^r"" " "'7"";' '">""" ""* "">"' """ *« ™nnltaneous forming of th™* ZLl^^ '7' ''"' °™'™">' ""' ■"»»" »' "" i.. question ;" a condition oH^tlHt',:^^^^^^^ T"""'"! "T" '"" ™"^ the hopixn-shapcd cavities in the assocLted mari" """"'"' ™*8<™» <" "'»' «''°wu by have been depositllt irr: , it I'l'^ i:,^^:/'"' ""«-'- "Rearing to serpentine-locality about to he described 1 1 T '" T" "'"''"■ "" °' *° that above, sonfetimes attainin;":,"!-:.!;:!' ^ tXTt' "The"" u'T^ ""■' the xij)por and lowor "•v„sum.hori/„iis fVmn ,- • ! mteival botwoen appear to 1. fi-on, ib.t^^ H yir tIu TL " ^""^^^"'"' ^-^^^ ai.sominat.d o.,p.,„„' ,, j f ^ ' J/,^ -uul. ioun.l n. ih.s u.t.wal ..ontaiu moro or less und shownuu.L , ;, ^^cu^^ iron .u druses in ,ho dolouuto, as obsorvod and ovn.udly ' ^ id h^ ", , T"''^ ^^'^--jbod as yellowish or brownish in c-olor, Mutt i;:'i„' '/;:!::,;::;:,''; :;:t'''^-'t" to ertend norlwL ■ fo Z,: ^V 'r"">- ,"« '";<"- " -tatcd. but it was said In 176 DR. THOMAS STEERY HUNT ON THE an interval concealed by soil, " first, a marly shale, then mixtures with more carbonate of lime, some compact, some crystalline, some confusedly aggregated, presenting cavities lined with crystals of that mineral, and containing also sulphate of strontian in the mass, and in the cavities. With these, and above these, are other aggregates like serpentine, marble, etc., with purplish shale or slate, which are followed by a green and blackish trap- like rock, as to appearance, but too soft for that rock." After this, that is, above it, is a mass which resembles the material overlying the lower beds of gypsum, and this last is covered by the upper porous dolomite. § 31. In a supplemer.t to the report of 1839, above quoted, it is added, "the green and trap-like rocks observed near the top of the hill to the east of Syracuse, have been examined, so far as time would admit. They are all serpentines, TAore or less impure, and of various shades of bottle-green, black, gray, etc. They all produce sulphate of magnesia with oil of vitriol. . . . Some have a peculiar appearance, like bronze, owing to small gold- like particles, with a lamellar structure, resembling bronzite or metalloidal diallago ; also other particles highly translucent, like precious serpentine, with frequently small nuclei resembling devitrifications or porcellanites, colored white, yellow, blood-red, variegated, etc. The grain of this is like common serpentine. In other kinds, the mass seems to be made of small globuliforn concretions, varying in size, being centres of aggregation. Some are of dark vitreous serpentine, others of the compact kind, the enveloping part of a light color." Vanuxem's farther notes, in his final report, add some important details to the ab'.ive. He says : " The great mass of entirely altered rock is a well-characterized serpentine, espe- cially when examined by the microscope." He mentions, moreover, the occurrence of mica, both white or light-colored and black, besides accretions which he compares to granite, and others in which a liornbleiide takes the place of mica, forming aggregates resembling syenite. He also describes granular carljonate of lime, like marble in texture, which " ex- isted as accretions or nodules, enveloped in the serpentine." § 32. I endeavored many years since to obtain specimens of these rocks, and through the kindness of Prof. James Hall secured a single mass of the serpentine, which contained small plates of a copper-colored bastite or bronzite. Neither mica, hornblende, nor any other crystalline silicate was however present in the mass, which was a well-defined ser- pentine, with some admixture of carbonates. It agrees «losely with the description given by Vanuxem, being an aggregate of grains and rounded masses of serpentine, with others of a fine-grained carbonate of lime, imbedded in a greenish-gray calcareous base. The colors of the serpentine vary from blackish-green to greenish-white ; it is often translucent, and takes a higli polish. An average portion of this rock gave to acetic acid, 34.43 parts of car- boimte of lime, and 2.73 of carlxjuate of magnesia, with 0.34 of iron-oxyd and alumina, leaving a residue of 02.50 of insoluble silicate. This was a nearly pure serpentine, as shown l)y its analysis. It was completely decomposed by tailphuric acid, and gave silica, 40.(i'7; magnesia, 32.01; ferrous oxyd, 8.12; alumina, 5,13 ; water, 12. '77=90.30. No traces of either chrome or nickel could be detected. One of the small imbedded calcareous masses or concretions found in this serpentine was I'nely granular, greenish in color, and was nearly j)uro car])onate of lime. * * For (kitiiilH of tliis miriKniliiio and itw analysiu, sw Aiiuir. .Tdur. Rcioiico, (2) xxvi., 20a, and Geology of Canada, 1863, p. 035. GEOLOaiCAL HISTORY OP SERPENTINES. ' 177 erall! Tf If' T"'"'t tf'"' '"^ ""^^^*^"" '' *^^^ ^^^^^^^^ ^^^^^^i^^ -e. however .en, pany.„s ..™,a is i„ ,h. fo™ of,h„ do„W„ caA„„.ter^'"°"' "■"1 '■»'<»"«'• 1"«™ with bitumf- III.— Serpentines in Euuope. § 36. Having- thus passed iu review some of the priuoipal facts known with re-ard to t "7" ^rT'""'' "' '''''''' ^"^^"""' -« ^^^"'-^ ^« '^^ considerati^ ml ame rocks ,u different parts of Europe, wiiere. as shown in the openin..- sections of t s -ay, they have long been objects of study, and have been alternat ly rega ^dTi^ '" nous and as exotic in character. o-iiutu as inaigc- * (i.'(ilnj.'y (,f CiiMnilii, lS(i;!, j,j,. ;i47^ ^i>J■,, t Amor. .I„„r. SH. [2] xxix., 284, mul xsx., 28(i. t !^oo llm autlior'H f"li„i„. and (io„l. Kssaj-.s p. ;!;«i. 8 Hull. Soc. UM. do l'"rnii(o, ISi; [2J, iv.j h;!7. Soc. IV,, I8y3. 23. ijii i\ 178 Dl{. THOMAS STKllRY HU^^'l^ ON THK i The hypothesis of the igneous and eruptive origin of serpentine is well illus- trated in the paper by Trof. Bonney on the serpentines of Cornwall, England, in the Quar- terly Geological Journal for November, 1877, supplemented by his later observations on the geology of that region, communicated to the Geological Society of London in :srovem- ber, 1882, and published in abstract in the Geological Magazine for December, 1882 ; in which connection should also be consulted his paper on Liguriirn and Tuscan serpentines in the same magazine for August, 1879. § 87. Bonney at first accepted the then generally received opinion that the crystalline schists in which the serpentines of Cornwall are included, are altered paleozoic, but in his latest studies of the region he announces the conclusion tnat i^hey are not paleozoic, but eozoic (archiean) and consist of a great series, divided into three groups. The lower one, of gri>enish micaceous and hornblendic schists, he compares Avith those of Holyhead Auglesea, and the adjacent shores of the Mervi strait, in Wales. The rocks of these localities, belonging to the Tebidian series of Hicks, have been examined l)y the present writer, and, by him compared with the Huronian of North America. * ^N 38. Above these greenish schists, in Cornwall, according to Boniu^y, is a black horn- blendic group, and a still higher granulitic group Avith granitic bands ; the characters of these two recalling portions of the Montalban or upper guessic series of North America and of the Alps. It is in the lowest of these three divisions, consisting chiellv of micaceous and hornblendic schists, that the Cornish serpentines appear, accompanied by so- called gabbros or greenstones. Bonney finds, with Boase and with De la Beche, examples of apparent interstratiiication and passage between these rocks and the schists, but concludes nevertheless, that there is evidence that the serpentine was introduced aft(>r the crystalli- zation of these, and that its eruption was followed by that of ' ibbros of two dates, and subsequ nitly by that of granitic and dark-colored trappean rocks. He throws doubt upon the ancient hypothesis of the conversion of hornblendic and pyroxenic rocks into ser- pentine, and supposes this mineral species to have resulted from the hydration of an olivine-rock, such as Iherzolite, which consists essentially of olivine with enstatite ; grains of both of which speiies may be detected by the microscope in thin sections of some of the Cornish serpentines. According to John Arthur Phillips, some of so-called greenstones of Cornwall are eruptive, while others are undoubtedly indigenous, and graduate into the crystalline schists of the region, llt'spectiug these, the writer said in 1878, " these bedded greenstones, with their associated crystalline s(^hists, appear to have strong nvsemblances to the rocks of the Huronian series, to which farther study will prol>al)ly show them to belong."' t § 39. Bonney has also extended his observations to the serpentines and associated rocks in Italy, which he includes under the general title of ophiolites. This luvme, and the kindred one of ophites (dreek, oithih's, a serpent), alluding to their greenish colour, resem- l)ling that of the skins of some serpents, has been t'xtended so as to include both true ser- l)entine, and the frequiMitly associated rocks which present some analogies with it in color. In fact, we pass from pure serpentine, and admixtures of this with carbonates, to serpen- tini. rocks including more or less of diallage, bronzite or bastite, and thence to aggre- * Amor. .Idilr. HcioniHi, 1S80, vnl. xix, ) •>. 27(i, '.'Sl. t lliirinT.V Aiiuuiii lieciihl I'nf 1.S78, piiun 3(is. GEOLOGICAL HISTORY OP SEIiPENTlXKS. 179 great group of rocks essentially made up of an anorthk- feldspar with a pyroxeuic element omL edt s^^^^^^ Z '^ '"^^""^* ""'■'^*^" "' ^^^^^^^"^"^^^«- ^^1 '^f ^'-- rooks were iTes ^ " " convenient though not scientiiically-defined name of ophio- ado p!er;n?e.?'T f , '" t'"" ^'""^ "^ ''''''" ^"""*^ ^^ *^^«« ^^^s, near Leghorn) was pects o 1^^^^^^^^ ' ?"'*'^' !" ^"^^ ''''' '^^'^'^y^ '- ^ «-"- —• His numerous speues of gabbio embraced serpentines, and the various diallagic, hornblendic and feldspv he rocks already noticed, of which the red gabbro, or sr^Mro ro.o, seems Imt a locallv d t colored and partially decayed form. The name of gabbro ha. come withm^iyl tCwis mean a diabase, but it is employed in such a very indefinite manner that^t would be we If It were dropped altogether from use. * It is often made to include the ^r^^^^ L e em^ris ::^^^^^^ ''^ -called euphotide, in which, as we aretold tL^MC vartyTf ticlin f r '^.rf""'" ^^^'""'^ ''''' ^'^' '^ «"- "--- ^o a compact IliTe d isU Jlh-d f''"V U *^'^^«^'^--^^'^^ -' - I have elsewhere shown, a compact mTi r^ls at We 7 Tr '" ''^ ""^'^ "'''''' ""'^'''^ ^^ ^-^l--- The two Z^r:I^Zru ' TT'^''^ "^ '''' "^P^°*^^^^« alike of the Alps and the MontXrato t ''"'""" "" """" """"^ '"'^^ '"" ^'^"^'^ ^'^^^ '^"^ ^^''- Berpi;^;e!^t t^^^' ■ "^T"'' -'^f " ^" ^^^^'^ "^ ^ ^^^^^ ^ I^^=™ -^ Tuscan r we. n ":" ;: "^ ^'r r-""^' "''•^^' ''' ^^^^^^^ ^« ^^ -^^^ ^^P-^^ larther on ^uanange^.n three geographical groups. First, ophiolites on the sea-coa.st west of riiiz,f ?""' '"'■■"? *'^- "^"^'^^""'^ ^^ '^'^'^'''''^ ^^^>"^ 'i-k-™!--^ -'-^« --— ^'. hornblende, L u ophane ..hlorite and saussurite. He states that the ophiolites of this redon are so ke lose oi Cornwall that he feels .justified in claiming for them a similar origin. In a se ond group, he notices the ophiolites of a region immediately eastward c J the first between G.noa and Spe..ia, which he describes as very similar to these. Bonne .:^ f r all ot these serpentines, as lor those of Cornwall, the notion that they liave l>een formed ^i^::TT 7 '77' T'^' "^ '''''''^'''''' ^«'"^^' ^ "^^^^^^^^ -h-h he -' ouves o have been founded on hasty and im,-.>rfect generalizations, and ro-ards them as generated by the hydration ol' intruded olivine-rocks. In the third -n-oo.;^ ica ^i", o^ the ophu>htes described ],y Eonney, he places those of Monteierratol' ^^ =Z n:^s ;;;: ^ •" "^T' "^T''-' ^ ^^-^^^^^ ^^^^ ^^-« ---^^^uices between t^X roeks „d those met with m the similar areas in Great Britain, and suppose an n rusion ot serpentine, or rather of olivine-rock, among crystalline s..hists. followed by " three distncts similar condUums and origin to those in Cornwall, North Wales and Scot laud, remarking that notwithstanding the fact that the Italian .:^7Zlt: 7^^^ *'^^" '" '''is •■nnmv'lioii, (',),vln, liiill. S,.,.. Gool. ,U, Fr (IS')!!^ xiii -w. „i i- 1 ,, iK'noous un,l So,li„.on,a,y Ko.ks .,r T„s,..„ v, il.i,l, ,8.11 ,!„ -Si) ' ' ''"'"""'" '"""""" "" *''° t (•.mtr,l,uti..n.s to tho History of iM.pl.otido a,„l Saussurito. A,„or. .Tour. S..ion,.o, Isr.S, xxv., 4,S7. ,gO DK. THOMAS STKERV HUNT ON TUB leas, assigned to the ce„ozoi. pericl, "they areprac.icaUy identW" «* ihe ,en^uti„os and gabbTos of more ancient tunos. ^f.^mputine with a caldtc cement, i 42. Bonney further calls attention to the breccias ^^-^P^ ^^ ^^^^ ,^^ serpentines found at various points with those Italian serpentrnes, -^^^^^^J ^ '^^^^^^ , J^,,,,,,.. have been brecciated i. .in>, so that it is possible ^ '^'^^^;^^:^^,,^rn.r:i., from unbroken or slig-htly ilssured blocks ^^^-^^'^y^"^^^^^^^ m" which and even to mixtures of finely broken serpentine cemented M' - ^onat. ^t _ he notes, here and there, iilmy patchc. of a seij.ev.t.nous '^:J^^^^2c^y,,,^, solved and again deposited. He believes that thj. ^^^^^^^^^ W^ ^^^^ ,,,, confirm a serpentine. The correctness of these views « .f «X:7;^°m^ s^i^of similar brec from my own observation, in the same reg-.ns, aad ^^J^^^ ^,^^^^^^^,.,,_ ^..^..^e cias accompanying the ophiobtes of eastern C anad^ Jr.^ .^ ^^^_ an important observation of a breccia m the vail y of 1 ic b a^ "^^^^^ ,i,te with lime- pentine, and consisting of cemented fragments oi ^^T^^^X^^o^ ehrysotile. * stone (alberese), the paste be! , traversed m ^'^^ ^^"" ^7. ^ '[^^'^^ of those Italian § 43. Bonney-s observations thus brmg us face to a e h tb^^. lc^^ geologists who regard cerUun of these serpentines as o ''-'^^r^Zt^ the .enesis of I having had an eruptive origin, although, as we shall ^^^^^'^^ ^^^^ of the these rocks differ as widely as possible from those of ^rof- Bonn ^ In a 1 International Geological Congress at Bologna m ^^^J^]^^^^, ^.^o.ico), had, under the direction of the ^ ^^ ^"Z^^Lion of the problems We extraordinary preparations ^^J^^^^ ,,^ ,_i,„, ,,,, ,,,,lished, show- offered bv the serpentines of Italy. A. map, ^.ili>.i.h.^ i , „p 1 1 111 lllth • ^^tllalities If the ophiolitic masses fbr the whole^i^om.^^ besides separate maps of particular regions on ^^^^^^ Molferrato inPrato, and Issel for the lUviera di Levante in I^uria a id ^^^^^^ ^'^^ ^J^^f ^ ,^, u, Comitato in Tuscany ; with especial memoirs on these districts, ^^^^ ^'f^^^^^ i„ „,any Geolo.icoIn 1881. Ophiolitic rocks are met with m greater o «- « *. ro^ ^ J^ localiUes from the Alps, throughout the Aponnines,^nd , i -^'^^ ^^ . ^ ^,,,.,, ,, studies of Taramelli, Lovisato, De Cxiorgi and ^' ""^ ^f'l^f^^;;^.^.^ a collection of those previously named, have contributed a great ^^ ^ «^ ^ ^ ^^ ^^^^ to chemical and ophiolitic rocks from various localities -^ ^^ ^^^ j ^^ w'uuf o occupy xnicroscopical study by Cossa of Turin, aided by M t n o ^ ,^. about 200 pages, illustrated with many plates, m the in. cpunto lished on luiiiau lithology. t . , . t 1 1 p ^^^ 5 44. Duving .;>» ln,en,»Uon,,l «,.*gi.al Co„g,v., a »p.«™ ^^^gh" ok l^.n,- sided ou that o.,-asiou. A d..|ailod ....ovt ol th.' pmcdm.' ..t lu^ "u = „ the n.i fa»i«,u.s or i,.,. B„....ti„ ",[, ';,^;:;: «:i^™v;; ^Lt^tui;, i>p. ^.^.w, GEOLOGICAL HISTORY OP SERPENTINES. 181 studios of Taramelli ou the Italian serpentines, pp. 80-128. It is impossible to speak too highly of the zeal, the industry and the sdentific spirit exhibited by the Italian geologists m these researches undertaken for the solution of the great question of the ophioUtes, which may well be held up as a brilliant example to be followed by other nations in similar circumst uncos. § 45. Mention should also W niad*^ of th.' Im.'f memoir of thirteen pages, in the French language, by Pellati, prepared for th(! Ueological Congress, entitled Etm/es s»r les forma- tions ophiolitiques de Vltolier in which are set forth, with great conciseness, the principal facts with regard to the geography and the geology of these ophiolitic masses, and the theoretical vi.>ws entertained with regard to them l)y various Italian geologists, .accord- ing to De Stelani, whose discussion is coulined to the ophiolites of the Apennines, the.se rocks belong to three distinct horizons :— 1. upper eocene ; 2. upper trias ; 3. paleozoic ; none of them pertaining to a more ancient period. These ophiolitic rocks form zones and regular beds in the midst of the sedimentary rocks, ^nd in no case plutonic dykes. The different varietit^s of serpentine, and of the non-sedir 'iitary rocks which accompany it, are themselves found in regular alternating bands. * ihe conception of this observer as to the mode of eruption of these rocks appears to bo essentially the same as that of Issel, Mat- tirolo and Capacci, to be explained further ou. (^ 91-93 and 100.) § 4G. The more recent studies of the R. Comitato Geologico, as announced in 1881, lead them to reject the views of De Stcfani as to the age of the ophiolites, and to refer the whole of these rocks in Italy to two geological periods. They distinguish ancient serpen- tines, probably pre-paleozoic, and younger serpentines, referred to the tertiary. The older serpentines appear in large masses to the west of Genoa, between the valleys of the Tolce- vera and the Teiro, and from thence are traced to Mouviso, from which point the ophio- litic group passes north-nortlieast to Monte Eosa, and thf.'uce, by the canton of Ticino.to the Valtelliue. To the same ancient series are also referred the serpentines of the north of Corsica, those of Elba in part, and those of northern Calabria. These ancient serpentines, according to Tellati, i'ollow the contour of the gi-eat zone of old gneissic and granitic rocks' which passes along the Alps, through Corsica and the Tuscan archipelago, and re-appcars' in Calabria. The older geologists, Collegno, Pareto and Sismondi. regarded the serpentines of the areas thus delined (in common with the others yet to 1),' mentioned), as having been erupted, like granites, porphyries and basalts, at various geological ages. Gastaldi," how- ever, as early as 18" 1, assigned the Alpine serpentines to a distinct pre-paleozoic horizon, which, from the association of the serpentines with vcrious rocks known as gri>enstone8 mpietre vcrc/i, he designated as (lie pietri-verde zone, and compared with the Iluronian of North America, of which he supposed it to occupy the horizon. ^ 41. Th(> conclusions 6f Gaslnldi as to the Alpine serpL'ntines have, according to Pellati, been conlirmcd by Baretti, and by Taramelli, the latter of wl'om cU>arly shows that the view held by many that the rocks of the pietiv verdi are carboniferous or triassic, is inadinissal)le, and that they belong, as maintained by Gastaldi, to pre-paleozoic or eozoio time. All of the ophiolitic masses west of the meridian of Genoa, as well as those of northern Calalnia, are, by Pellati, included in this class. * Holl. 8or. GooloKica Italiana, i., pp. 20-3;?. 182 mi. THOMAS STRRRY HHNT OX TIIR To tho oast o{ this monclian. acvordin. to Mlati. .o Unci th. n..v.M- or ^^'^^yj^^ pontin,., in.luclin.. livst, thoso of .ast.vu L.guna, whi.h have th.r .roat. t d^e op L-nt along a lino runnin, north-northwost from Spo...a. and sooond, ^;' ; ^ '^ ^^^ ^^^ pvoso Aponninos, oon.isting of a groat nun^hor of small massos s^atton-d b. u Fl o n^ ^ Ina Eoiio in Emilia. A third .roup in. ludos tho n.assos of s.-rpontin. ' > /> ^ ^ (Irossoto^nnl San Miniato, m adduion to whuh tor.iary sorpontm.s aro nu bo . u u Ul k^ and in tho uppor par, of ,ho valloy of tho Tihor. Furthor south, othors ^^^^^^^ La.ono.ro in tho Busili.ato, iron, whuh point to Noopoh a ^^'-^^^^'^^^TI^ serpontinos is tbundalou. tho uppor part of tho vall.y ..1 th. ..nm. ^^ --J^^' po^inos, thus indi.-atod by FoUati. aro. a.ordin. to him, ..norally lound m tho nudM^M h. limoston... argillitos, and sandstonos of tho oooono, oxoopt in tho oaso of tloM l!;;."" aross^to Ind San Miniato, tho outorops of whioh aro oHou soon nsmg out oi pliocene day. and sands. IV.—rvOCKS OF THE Alps and the A^EXNmE^!. ^ 48 Before proc-oodin. farther in the dismssion of ih. Italian serpentines it will bo wollto <^ot a view of tho present state of our knowlodge of Alpine .oology, and especially of the c^iolusions and generalizations of Gastaldi. Thoso, so for as th.- Ali>ine serpentmes are concerned, aro, as we have seen, accepted by tho ('omitatoaeolo.K.vv.Kl his .-on-oded it is difficult to escape his wider genorali.ation whi,h brin.s tho whole ol tho so-called tertiarv serpentines of Italv into the same oozoic hori/on with those oi the Alps. If wo o-o l,arkward to the early history of Alpine geolo.y, we shall there find the ori-inofthe%vell-knownhvpothosisthat tho crystalline stratiiied rocks are but portions ofmleozoicor more recent" sediments which, in certain parts of their distribution, have undergone a proce,ss of alteration or so-e.llod metamorphism. The infra-p.-Hion ol the uncrv^t.llino to tho crvstalline ro.ks m Mont lUau,-, first noticed by de Saussure. was thus explained bv Bortrand"; who su.gested that th-so erystalline s.hists wore altered roeks ot amoro recem date than the unerystalline mesozoie strata of C'hanumix. Ihis notion was adopted without .•ritieal study by Kel\.rstein. Murelnson. Lyell. Studer. ^>smondi and L he do Beaumont. am.Ut, aiul flmniiral an.l Conlo^'i.'al I'^snys. pp. ;!H7.:!;!!». n GEOLOfilCArj HISTORY OF SKIJPKNTINES. 183 in 1H71 and 1874, cntitlfcl Sfin/ii irfaloiiiri ^iille y\l/ii oirldrntnli ; in a letter to de Mortillet in 1872 ; in one to Zczi in 187t;, and linally in one to Sella in 1877, with a postscript in 1878. * Tliese various papers are illustrated with munerons maps, plans and diairrauis. In attemptiu!? to <,'ather from those sources abriel Mtatementof Gastaldi's conclusions as to the H'cology oi'the Alps and the Italian peninsula. I feel that 1 am both renderinii' a veritable service to sciiun'c and paying a tribute to tlie memory of my honored friend and correspon- dent of many years. § 50. The S/ni/i'. etc.. contain, liesides (histaldi's own descriptions and se -tums, many important historical details and extracts from the literature of the subject. In tiie second part will also bi' found reproduced two engraved sections, the one l)y Gerlacli. from Mcmte Rosa, by Varallo and the Ivago di Orta to Aron.i on Lau'o Maggiore, and the other t)y (*arlo Xeri. from tht» same point, in a (flurso more to tlie south-eastward, by Valsosia. to Monte Feiiera, and beyond, t A tomparison of these sections with those described by G-is- taldi, will be found of much value lor the elucidation of the questions 1)efore us. Start- ing from the rr'ul(ij.'i(( drs .\l)ic.s cotticnncs ; li-ttru il M. do Mortilk't, Ceiiiptcs Kciidns do I'Acad. dt's SciiMuv.-i do Turin, vol. vii,L'S iivril, 1S7U'; Uy s and liivuivs a s.rtionlrom Monto Bracoo throuo.h Mouviso and Monto I'olvo, akmg tho upp.r part of Iho valey o tne To. and the vallev of Varaita, to the frontier. ITis conclusions from the study ol all these sections may be t"hus sumnie.l up : The crystalline rocks of the Western Alps a,y classed iu two oTcai croups, the lower of wlii.h (the central gneiss of von Ilaner.) was cl.>s.n.becl bv (la^taldi as ihe ancient u'ueiss, and by him compared with the Laurentian ol North America It insists chiellv of a hi^'hly feldspathi. uraniti.^ uneiss, sometimes poi-- phvritic or ulandular. =u.d includes bands and lenticular mas.ses ol (piartzite and crvstaUine limestone, with white steatite, and -mphite. lieposin- upon the ancient ..,H.iss isa.vreat and complex uroup, desiH-nated l.y«( histaldi as the •• newer crystalline series •• which, from the frequent presence theivin <.f serpent ines. diorite.s, diabases, and related rocks of a -reenish color, is also called by him the x-'c of the o.,.een8tones, or the ^'"''V-il"ln a ovnerali/ed dia-rammatic section which a.vomi>anies Gastal.li's last pub- lished statement, (his let er to S dla in! s7S.) the iirst divisi of sclusis. wh,e,. are placed above the reeeu, -nciss and -■'aiiite. Finally, the whole series is overlaid l.v the uncrys- lalline sedinu'iits of the anlhradtic u'roup, of earboniferous a-'c vN .-..;. The lithoh.-ical chai'acters of the lower pari of thi> vast scies of newer .rystal- line sehists aivsulliciently well ddined in the various see,,on.ali-eady no,ieed. .\s regards those whieh immediatelv su ed the serpeutiuie. ehloriti. and tale-Mhist /.one. ,he gn.up ol ••niica-sehis,s-ofXeri. the-reeent o,,„iss;,n.l uM'aiiite- of (levl.ch and (lastaldi, we get additional li-ht irom various passages in the writin-sol the latter. They are spoke, of. in oim place. as-neissK mica-schists more ,,r less rieh in hoi'iihlendc in whieh. at Travers.dla, aro also inelnded seri.enlines. Mlsewheiv, th.' I'ocks of Ihe same area are successiv.'ly -■ailed luica-schist. ivrent uiieiss and miea-.schists, u'lieissic uiica-sehisis. and also, a. very mi. a- eeous-neiss. often passiii- i lit o mtea-sch 1st and sometimes horiiMendic. With these, or with the lower |.or,ioiis of ihes.u'ies, aiv associate.l ufanilic and s\eni,ie ro.ks which, in the opinion of (!a>ialdi, aie not erui)tiv.-, but the result of lo.-il modilicatioiis of the sur- GI-lOLOfrTOAL HISTORY OF SERPENTINES. 183 rouiulin. To this succeeds a-r.-at l)readth of the newer gneisses, in which is iii.lud.'d a large dyk." of meh.phyre, .'vid.'utly of eruptive nud posterior origin, and. farther to tlie westward, a mass of syenite, which is extensively ([UMrried. and has Ijeen studied with great care and descril)ed by Co.ssa in liis work already mentioned. I had the good fortune to visit this well-known region in tS81, in company with f^ignor Quintino Sella. The granitic rock of th(> eastern part of the section appeared to be a part of the ancient gneissic series so largely developed elsewhere near Uielhi, and consisting of reddish gra- nitoid gneisses, sometimes hornblendic. hut si arcely mica.-,'on«. often thinly lianded. highly contorted, and indistinguishable from much of the L'-,ieiss of the Lauivntides, or of the Soutli A[ount;iin in Pennsylvania. (\ist of Srknylkill. Inte.rstratilieil with it. near Biella, are beds of coarsely crystalline impure limestone, holdin-i' grnphit(>. mica and hornblende, and resembling closely some Laurentian limestones. I'llsewhere in the Alps, it may be noted, similar gneiss(>s include serpent inic liinesiones. as lor exnmple tli(> pale "Teen ophi- calcite found by Favre in the gneiss of MaUeubach near Lniterhiunnrn. which is indis- tinuuishable from that of the Laurentian of Canada, and like it cmitains Eozonn Cann- (/iiisr.j It is well-known thiU similar serpentinic ai<-gregales are often found with the limestones in the ancient u'neisses of Scandinavia and Finland, as well as in North America. ij •")•".. This ancient uneissic series in the Biellese is directly overhiid hy the ophiolitit; and (licn-itic belt (pietre verdi). and this is fallowed to the west by the newer li-neisses and mica-siliists. which cannot be distinguished fnnn those Inund in the vicinitv of rhiladelphia, ()!• in the White Mountains of New Hampshire, which I have called M(intall)an. The intruded mass of syenite, made up of reddish nrtjioclase with some nllijle, hornl)lende, and a little sphene, presents, in the extensive (piarries which 1 visiied. tlie massive charact(>r and the comparative homogeiK-ousness which helone- to :i pleutoiiic vock." The usually ureat breadth of ophioliiic rocks met with in this part of ihe ,\lps is here, us pointed (Uit to me l)y Siii'nor Selln. rai)idly reduced, to ihe southward, hy ihe encroachment of the newer y-neisses on the west w;ird side, and where the crystalline rocks sink hcneatli the alluvial j)lain, does not excede a kilometer. These relations suugest a transverse super- posit itui of the newer yneiss series alike upon the ophiolitii' group and the older gneiss, of which we shall tind evidence elsewllel'e \^ "Hi, It has been seen that the ilcsignalion of /y/V/rc ri-r//i was hy N'eri restricted io the ophioliiic yroup henealh llic newer uaieisse-;. which he referred to a later and distinct iicoloyical period ; ( iastaldi. on the other hanlween these inid ihe anihracitic .series, with their included gypsums and dolomites. The grounds of ' 'iiistiilili.Sliiilii, etc.. pnrl I., jip. I! iiiul 'Jil. t ]''uvn>, Uocliprdies gi'ukiai(|iu's dans la Smeic, cic, iii., il'.'n, uinl iilsn t luan. niiti licel, IvsHiiys, p. ill'.', .S'c. IV., ISS;!. Jl. mi THOMAS STHKKY IITTNT ON TIIE 186 p 1 4 ^ n... lower opliioli'i'' ^•*^i^'^' ''^^^ ,....uv al.o alike, amou. .ho ^^^^ ^l^;;^;;;:;^;: ,,, aolomiies that w. llud tlu- lasi Innit i. .avs OastuWi, - in .•o>Ua>t with the ■■> .muu. ^m ^^^^^^ ^^^ ^^^^ ^^.^^^^_ ^_^_^.^^. . .,,,^^^ oHho sorpeutinous ro.k. whic-h lor ^;-;''^';;;;;;; ^j,^,,. (;,,,,id, ,vas disposed to plaee iu ,,,s in 187± in his letter to de ^^^^^^'^f^^^^Zon ol' the upper sen>enlines. lie, , separau. .roup the ..rystalHt.e se usts aW ^^^^^ . ^ „., ,.„,, .,, „,. .i.nv - .rdi, Uo. ever. sul.se4uentlv i.uluded the -1-1^ o j^^ ; ^^ ^,, .j^,,,,,, ,.,,<>w this ho, ,zon. , ,T. As will he made a,n-v.d -he s.h^ts , a ^_^ ^,^^^ ^ ^^^_^^^ ^^^^ ^^^^^^^^ ,,. ,>o, to he separated innn those aho^e. X h ^^^^^^^^ ^^^^^^^^^^ ^^ ^^ ._,^ ,,^^.^^. ^„^^^ .j,, ^i,^, .,oup. ovorlyui. the younger ^t>e.sses, l.u ■ :„.^,„,ii „,„,, At other times, „,,, ,^,utoli,io .,.oup under the --;-;;;;" ^ ;,„.,, „,„„, „. .vht,h t, was em- Uastaldi us..d ,ho .evm .d' ptetre venh n. u ^^^_^ ^^^^ ,^^ ., ^^,,,^ ,, ,,,^^ ,,^,„, ,, x,.ri. lie speaks in 1ST4. o th. p. • > ^^^^^^^^^.^,^ .^^ ^^^^^^ ,u.ss, wh.-h l^"'" ^ ' ; ,„ .,,^,„^, .,• ,uis newer .neiss are older.- He s.ys lavth.r: • 1 wtll not assert ^^jtZlA alwavs he pva-tieahh. to dis- ^ ^ ..,„,,.„ai, nuxod with tho.. oi tho ...ore -;■;,.,,,„ ;,,,, ,„. u.e .ro.u.d, the H„.u.sh,hen.pe.ro.raph.oally;h.U .ono - ;^^ diMinotiouisnotdillieult.ona.vou,.t ol ,1. " " ' , he ohh.' -noiss, however wide its theo,h,.r ehara.-.>.'istie ro.ksof,h,. .Mn-r-H,>^uh.l ,.K„.ul is oen.rallv un.nix.'d wi.h oti.er rorks. ,^.,„.,. ,„„. ,h„ vountivr -iiieiss and '.s. Tl. newest erystall.t.e P-P' -'"'-7!' ''^;.'\. • '", ^ev lustro.t. sehists .i.:..his, ser.es, is that or tl... ^-ilU^t^^eose s, ns > la ^..^ -^^.^^^^.^^^ ^^^^^^^^^^ mi.aeeous lin.estone. hand,.! and ^' ' ^ > ^ ^,^,,„ .,/„,. „„.,,„. ,Vou, Turi.. to the spiouous ,u Alpin.. ..olouy. lln-s.- .0. U • u ^_^ ^^^^^^ .^.^_^,^.^ 1'-" 1> ^— •• -'> -V''^"''^' '" n!. .: . ' s ,0 ,h,s ..mi.e series o,' newer , ,,. Th. vast thi-kness ass,.,e.d U v a nou^ ^^ ^^^ ^^^^^ ^^ ^ ,„„,vkahle laet i>. their ,,vMalln.. s,l,i.ts. ,.ounti.,u- ho,,, ih. an...... u^ ^^ .„....„,ive /ones or groups in .he s,.,.,ious ahva.ly ..ol...'d. (.aMald.. ... • .. , ,h.o ue^l.'vs. ol' whi.h s..Mi() moters, ,„,.,i .,ne, uel.uhnu ih. upp.-r !us..o..s - "^ . ; ' ^ ,„,, ...rdi : apparently ,„. „„„.„,,,. ,,, ,.,,n,.d „> .h. low,.,, -l''' -;3„:j J, J, ..,,,.. ..P Ih,. n.id.lle -i-l.oui ,n,lu,Un. .h. von,,.,.,' ......s.. 1 • .^^^^^,^ ,,^„„„, ,i„.„.„a, and Kl..' .le ,,.„np. ■!■.. tie. UPI-' ^vonp. a> s,vn ,n .1 ^__^^^ ^^ ^^^^^^ j. _^^,^ _^,^ ,.„,^ P„.,,„,„„„,.H-,..da v..,.,,.al,h.,k„..» ol „o, l,s '"'■ " "'-^^ '"■'■" ^"' ''"':"■""' ''':'"'T;;! 'w" !'m''\h. a„d.h..s,.elions as yet noticed .h. , ,;o, \V,. hav,. li>,lM.,.,o .pok,.,, ol Iho W , ^„ All . . ^ ^^^^^^^^^^^^^^ ^^^^^^ „ X.-.1 ,. -h ., wa,.d ol La.o Ma...o,.e. 1 .0 ,..a ^ -• __^^_^^^_ ^^^^^^^^^^^^ V,„„„au Alp. puhUslKd ,- i-;';-i^. '-h,.a..s ,h , _ _^_^ ^^,^,^^ .,. ,,,„ ,n.l ^le.w> lie. san.e o.^der ol Mi.ve»,o„ as ,hal laid .lou „ U)^' ''________ ,_ * Siuilii. I'lirt ii.. !'■ '■'!■ . I . , ,. , ,,„„„, ,|,.,,l,,.,i.,.lH. fluTMrla^UiUl.. a-f (M.Tlvir|,i~,.|,-fn^,l- ,is,.l,,.,,Nl.,K.ela...lnl,v.,W,.,,..Vlrnn.,.l.^....M.Alrn;U-M. v GEOLOGICAL HISTORY OF SHIM'ENTINES. 187 various liToups, as iudicatccl l)y vou Hauer, are as follows : L The iiucicnt gnoiss and granitic rocks, dosio^nated by him as ilic ccniral gneiss; 2. Greenish schistose rocks, de- scribed as liornblendic, dioritic and eupliotidic, with serpentines, chloritic and tab-schists ; o. Saccharoidal limestones, more or less niicact'ous, witli talc-schists: 4. Serpentines, cuphotide, diorite, and talcoso and chloritic schists, as before ; 5. A iiiie-i>riiined gneiss, designated as recent L-neiss ; and t). Mica-scliist, with hdrnblendic and rcld.spalhi(^ varieties. AVe have evidently here the same great pielre-verdi zone as in the west, comprised between the older gneiss and the younger uneiss with its attendant mica-schists. There appears, however, a ^■onsidera])le development of crystalline limestones in the midst of tlie pietre verdi. § 01. Further lii-'ht is thrown upon the question of these crystalline rocks of the Alps by the ol)servat ions of lii-nevier, Ueim iind Lory, especially as embodiiMl in an essay by the latter on tlie Western Alps, published in 1878. and in a study of the u'eolou'y of the Simplon, 1)y llenevier, in the sam(> year. * Accordina' to Lory, the ancir'Ut crystalline rocks, designated by hiiu as the pn'miUve schistK. an seen in tlie Simplon. and elsewhere in this region, include three groups, in ascending order: 1st. The staiiv of tlie ii'i/rias, prop- erly so-called, includinu' varieties from the hi<>'hly feldspathic and massive granitoid gneisses to others less feldspathic and more distinctly lamiuated. 2nd. The stance of the mini-schis/s, often uarnetiferous, which embraces, liowever, alternntinu' beds of ss impren-nated with carbonale of lime, and )ry, is but a uiranitoid variety of talcose or chloritic e'lieiss. subordinate to tln' talc-schisi static, and passinu' in- sensibly into the lahose and chloritic schists, with which it alterna;es. Ii i,s not, there- lore, as 'y (lerlach as the li'neiss of Aniia'orio, to which t his eding mica-s.hisi s. ol'teii uMiai<'tirerons and i'al<'areou>. wilh alternatinti' u'ueiss and limoloih' bands. Iia\e also a L;i'cal volume. The hovniileudic schists play a less imi>or- tanl part in the scries. Thouuh these sonictinu's conlaiii a little mica, m' a liitle chlorite, chloritic schists ure lari'. and the siau'e of the talc-schists, indicated by Lory, is not iinMi- tioiied i(y K'enevier in his description of i he Simplon. s^ ti2. The leiin ol primitive schists, as employed b\ l/U'v and li\ Kciic\ ier, is not ex- tended to the e'rey lustrous schists, alreaily nolii'cd as lormiiiu' Ihe uppiT [lart of the great series included by iJastaldi in the pieire verdi. These upper schists are l)y Lory reeavded * I'M^iii siir rerM_'ra|iliii' il«'- Al|i'< .> ■•■i'l''nliil('< \k\v <'Ii!Ii1i'~ I,.i|'\ , p, Tii ; I'aii-i ini'l i eciinlilc, 1S7S. M,),) StrMl'lllri' fil'llle^'iilUl' '111 llUlfc'-ir ilu Silll|i|.MI. rlr.. |i;ir i'i. Iti'Ui'UiT. I'.llil. ill' hi -ei'. \ ail' l"i>i(\ cll'-i srit'llrCS iii.titr elliw, Vol. xv., No. 7'.i, I ,gg I>1!, TUO US STKEIIY HITNT ON TUB . altered tri.. a vie., in ,vhioh Kenevior „c,„io.«. They »;^ [-^''^Xl':" glistening, and taVo^e in aspect, an., have been vanonsly d.^|; - - ^^;^^^^ ^ and a,gillo-taleo»e «hi»ts, heine; .ometunos. ^u--eordmg lo Lo.y. tiu, u sulphate of lime (kavstouite), and is accumpau.t.d by -''^-f ', j'" \ " '^^^^.t^.i^. ,hlo- .ilicatos are also Ibuud in this gvoup ; nodules oi'tale are nnl.edded '! ^';^^t^^^^_ rite oeours in veins and layers, and beds of seruentine (and ol eupUotide. ae.oidmg to Gas taldi) are interstratilied ^Yith these shining argiUo-taloose sehists. CS. The reseniblanees in nuneral eharaeter between these upper argillo-akosseluts with chlorite and with interstratiiled serpentines, and the lower or lrut> P-^---^ o e^ are obvious. Lorv lu^s moreover remarked the likent^ss between these upper s,.lnsts with limestones and th'e miea-sehists with limestones in. the horizon of the newer gneiss series, ineluded by him in tlie primitive sehists. as leading to the eonfounduig ot he two^ Th . resemblance, ho suggests, " may have thown some obscurity upon the relations of tW various rocks, and the structure of tlu, region It wUl not have escaped the notice o om readers that in the description of the section of the Simplon there is no recog-in ion wh.d- ever of the great mass ol serpontmes, euphotides and other ophiohtic rocks belonging to the pietre verdi, which elsewhere are ibund at tlie base of the newer crystalline schists, occupying a horizon between the older and tlie younger uneisses. §04 Ir will also be noted that Lory plac. a liorizon of tah-schisl., with chlo it c rockl etc., at the summit of the newer gneisses, and the view naturally su^c^s se f^Ou^ Lory has himself confounded the lustrous schists ..f tlie upper series and then n. gios m rocks, with the great lower opluoli.ic zuu.. This latter would appear lobe -antu.g m c section of the Simplon, where it is not noticed by Uenev>er. Lory thus places abcne the younger .neisses a talc.hist series to whidi he relers many o the types ol ro.ks niet witli in the great ophiolitic and tah-schist zone, whu^h e sewhere under les the..e younger o.„..isses, and in whi.h th- i,n...,.'ines are probably mc nde.l. In this w a > ! . 7- V 1. .tw,...>. lorvnid all the (.l.s.Tvers lutherto mentioned is thi' apparriit discivpaurv between iAn\ .uni an , i • ,i explained, as suggested by the present writer in l^sl. "fh. rela-oMs ol>served in the Biellese, as already noticed, suggest that the younger gneisses were deposited un.oniormably, alike upon the older gneisses and the great ophiol.ti. uroup, as is the .ase ,n many other "°'Tii^ Li like manner, according to Lo. y.lhe lustrous schist,, themselves, with included serpentines (which he regards as eontemporaneuus eruptions) vst directly upon the ancient ...n..iss,.s iM the Levanna, between Siisa and Lanzo. ( Mh.T .vd.uc.s of a want ol .•onloi- mitv l-Hucn (h's.. various gruui-s of an, i.ut s, hi.is in ih. .Mps ar. not wanting. At the (-old.. Mom CencvrcasdcMnbodby L.n. .here appear> ihmugh th. lustrous schists a Hull. fof. K.'iil ill' I'l-illirt^ X., '-'^1. GEOLOGICAL IIISTOKY OP SERPENTINES. 189 great " mass of non-stratified rocks, comprising eiiphotides, serpentines, variolites, and various rocks of passage between these types " These ophiolitic rocks, which correspond to the lower part of the pielre-verdi zone of Gastaldi, are regardtjd l)y Lory as eruptive, and have not been recognized in his scheme of the divisions of the primitive schists. Their appearance among the histrous schists is thus, according io him, an irruption in ihe midst of the trias, instead of being, as we should rather regard it, a protrusion of a portion of the pietre-verdi zone in the midst of the lustrous schists, which are here unconformably superimposed upon it, as elsew here upon the ancient gn(.'isses. § 06. The history of the upper or argillo-talcose schists of the section under considera- tion will l)e found discussed at some length by the presiMit writer in a revi -w of Favre on the geology of the Alps in 1872. It was there shown that thes.', though very distinct from and unlike the underlying micaceous, hornblendic schists and gneiss, are really crystalline schists, and very unlike the normal trias of the region, to the horizon of which they had been referred by most geologists. The section of them afforded by tlie Mont Cenis tunnel was then and there discussed, and many reasons were given for rejecting the notion of their triasslc age, and for assigning them to the eozoic period. As was shown in a sub- sequent note to that review, Favre, after publishing his book in ISOT, was led to adopt th(> view advanced by Gastaldi in ISTl, that tht^sc S( liists wcn> prc-carl)onifcrous, thoun-h probably p-ileozoic, a conclusion which the latter sul)scqiuMUlv e^ichanged for that of their eozoic age, as maintained by the present writer since 187-. ^ § 6Y. The section traversed by the St. Gothard tumid furnishes important details for Alpine geology. This work, ])eginning at Gosclienen, on the nortli, ends at Airolo on the south side of the mountain, the entire distance Ix'iim- 14,!t2() meters. The first 2,000 meters from the northern portal are in the massive rock of tlie Finsteraarhoru, called by various observers granite or granitic gneiss, and by Staptf regarded as an older gneiss than that of the remaining part of the section. IJetweei this and the mountain of St. Gothard is included the closely-lblded synclinal basin of U^seven. whih' the southern portal, at Airolo, is on the northern side of tiie simihir basin ofTici lo ; thearcat intermediate mountain-mass of higlily inclined and faulted strata, prescntina- a fan-shaped arrangement. Tlie basin of Urseren holds, folded in gneiss and mica-schist, a grou^) of strata consisting of argillites, sometimes calcareous and often grapliitic. with grey lustrous, unctuous soricite-scliists, together with quart zose layers, andotliers whiih. from a development of feldspars, pass into an iuipc't'ect gneiss. Witli these are iulcrstratiiied u'ranuhu' cryslaliiuc limestones, white or banded with grey, with dolomit;' and karstenite. Some of the limestones included in this synclinal have allorded iiulisliiict organic lornis. ami the series has hecn referred, like tiie similar rocks noticed in previous sections, to the mesozoic period. A repetition of these is met with in the Ticino basin, on the south side of tlie mountain, .\part from these, the great mass of strata along the line of liie luimel consists of niicaccims aiieisses and mica- schists with hornblendic bands, the wlmle liaviim' the rjiaraelers of the younger gneissic series, and very distinci from the older gneiss of the noil iiern porlioi;. I If lliis latter be the central gnei,ss, the })iel re-verdi zone is luTc al)sciil. I SHI. " .\iiitir. .lour. SciniKv, (3) iii. jip. l-l."i, nl.'^o Cliiini. and (iiMil. Kxsays, pp. I)3.'i, :!l!() ami ;II7, t I'or full ili'iailx ^t. Got hard section, will bo described in jnirt. VII. § 08. AVith regard to the presence of granites in iliese regions. Cordier, as cited l)y Lory, long ago assorted that true granites, occurring in veins or iransvrisal inclusions, are rare in tlio AVos' "" Alps, lie, however, excepted some masses, of Avhich t he granites of Baveuo may bo taken as a type, and others, which are ratlier veins of segregation (endogenous) than of injection. * For the rest , CNnxIier reii'ardod i he uranit es of t lie Alps as stratified rocks. Gastaldi. aoing still farther in his protest against plutonism, admits, in the regions exam- ined by him, none l)Ut stratified rocks of aqueous origin, and has included in his sections masses that I regard as igneous a)ul intrusive rocks, but which are by him <'onfouuded with triie indiavnous gnoissic rocks under the title of " recent uiieiss aiul granite." As regards tho porphyry mentioned in the sections of Neri as above the rei;ent s'noisses, and that placed by Gastaldi al)ov(> the lustrous schists, it would appear that the latter em- ployed this term in a very vagiu' sense, since bespeaks of tlu> feldspathic and quart zil'erous porphyries of this region as presenting great varieties in structure and in composition, and as passinu' into other rocks, notably into granites, from which it is often difiii tilt to separate them, t lU^ seems, under the general term of porphyry, to have included both stratified rocks at dili'erent horizons, and intruded masses of various kinds. § iJ'.t. From tho various descriptions aiul S(><'tions of the Alinne rocks, whicli we have here considered, it appears that they may Ite includi'd in four distinct groups, which are as follows in asccndinu' order :— I. Tho central or ancient granitoid i^iiciss, with o ■casicnal (piart/.ites and crystalline limestones, bearing graphite and many crystalline minerals. This group we refer, with Gastaldi, to tlie Lauren; ian. II. The groat uToup of thepiotn* vordi ]iroper, in whidi, Ix'sidesserpentim's ami ophio- litic rocks are included ])ands of limestone, and also appareutl v <(M'tain a'noissoid rocks, the protoii'ine or the talcoseirnoiss of I.,ory and Taramelii. {ii\\. 7>.l it is worlhv of remark that although Gastaldi. like Neri, Geriacli and \dn llatier. pke I'd the great group of recent gneiss and mica-schists al)ovc the true pietn-vcrdi /one w iiirli he declared to be com- linod between the older aiul the newer gneiss, he. in his last published sketch, indicated besides this, aii'iliier horizon of "recent !:neis> and liianite'' (not eisi'whero noti<'ed l>y him) inti'rcalated in the pielre-venli zone, as thus limited. :iiid iirol>ablv enrresiiondimi' to these talcose gneisses, 'i'his second or piein'-\-erdi eToii[i. we refer with ( I.asialdi to the lluronian. III. Tho youne'er aiieiss and iniea-selii>t series, with hoinlilendie varieties and interca- lated erystailino limestones, and in some cases with ser|ientines and eui)hotides. This group, upon the litlmlogical characters ol which we have already insisted, {§ .'>i], 'i">, 07) we regard as tho reprosi'ntative of tho Mouiallian IV. Tho ui)por luslroll.^ schists with uvpsuijis and karstenile and tale, willi inler- * SiM' tliii luitliiir in Chciii. uiiilOiiijI. KsHn.VH, |iaM'i' l!.'!l. t Siii.lii.cic, luirt II., J), :M. GKOLO(;i''ATi HISTORY OF SERPKNTINKS, 191 stratiliod sorpentiuos, quartzitcs, often sandsto stones, and banded and statuary niarljles. This nes, arii-illites, doloniit es, raicaeeons lirae- s(Mits many r('S('inl)lances witli tli rica. In it (■ li-reat Lower T •oup. as W(( have already indicated, pre- ■onic or Taeonian series of North Ame- ar.' included by (lastaldi, the crystalline limestones of the Aj • ,1 ,, , . ,, - - ......-., >,. 1,1,. ^puan Alps, which yioldthestatuary marbles of Carrara and of Mass:.. § 70. In the Western Alps there is. so far as is kuown, no evidence of lower paleozoic ro..ks, the sandstones with anthracite, ^vhu■h su-eeed the crystalline schists, containin-v in many places a carboniferous ilora. Tlie same, a- vordim-- to tiastaldi, is true in tlie Maritime Alps and the Apennines, wh.nv, in many cases, he linds the crystalline .s.^hists overlaid bv the anthracitic series. Thus in tlie valley of Macra. above the serpentines are found .alcareous schists with <'rystalline hmeston.^s and quartzites. whi.Ii are suc.-essiv.'ly overlaid by the carboniferous sandstones, the limeston.vs of the trias, with their ch;.r;,cterislic fauna the has, the cretaceous and the numinulilic beds. At Torre Moiidovi. tlie serpentines are over- laid by fossiliferous triassic lime.st.mes, while in the vallev of Bormida they are directly succeeded by the marls, sandstones and cono-lomerate.s of tlie lower miocene, and in the valleys of Stn libra and I'ol.evera by the albere.se and the madn-no of the ecene. The supposed pre-carboiuferous launa found by Mich.dotti in the limestones of ('hab:.rton, has. on fur- ther examination by Prof. Meneghiiii, be.Mi shown to be of triassic ai-v. * §-\. Passing now from the mainland of Italy, we come to ( 'orsica and Elba. The ser- pentiiu's of the former Island have long- been known to geologists, aiidhav." within the last few years been especially studied by ITollande. Coquand, Dieulefait and Lotti Coquand, who described th(" serpentin.'s of Corsica in 1870, and who. like lloUiuid.'. re-ards them as eruptive, supposes them to be in part very ancient, and in part tertiary, since accordiiu;- to him. some of them ovrlie the nummulitic beds, t Tellati. whose essay we have alivady cited, refers however the whole of the serpentin.>s of this island to a pre-pal.moic period, and Dieulefait, who described tliese rocks in ISSU. J declares that Coquand's r.>lerence of the s.M'peniines found near Cort(> to the tertiary is b.Ms.'d on an error of observation. He moreover asserts that the serpentines of CWsica are stratiiied sedimentary rocks belonninn- to a single geological horizon, al which they may be traced continuously for a length (tf more than :.'(I0 kilometres from Cor,so along the northeast .oast of ihe island. The ideo- logical succession, acco-diny to him, is as follows:— ], stratiiied protogine ; 2, i-'neiss ; 8, lustrous schists; 4, salassy, Iml e-ranulai' varieties are mi'l with iiidudinu veinf' of epidote. others with altered crystals of olivine, and also ophjcalcites. 'i'iie u'neisses beneath the serpcntine- * (iiiMtiiMi's Idler In Zezi, in ]S7S, iilrnndy citiMl, t < 'eilllilllil. Bull. Sill', (iriil. lie r'nuife, i:',) vii. I nielili'l'nit. Ciiinpltw Keiuiiis ilo I'Ariiil. dcs Sciences, xci., |i. KHHt, '/. I.iilli, AinMinli ( ieiilegici snilu I'liiHiiii ; Itell, ilel Coniitiito Uooliigifii, unue iss:!, No. ;\~\, 192 DR. THOMAS STKRRY HUNT ON Till'] zoin^ pass into quartzoso mica-schists, often includino' almond-shaped masses or segrega- tions of quartz and feldspar, sometimes with largv phdes of mica. It would appear from the descriptions of I,otti. that the.se serpentines of C'orsii'a belong to the upper horizon delint'd by Crastaldi, above the recent gneisses, and in what we have designated as the fourth group of Alpine crj'stalline rocks. (^ t'.ii) The underlying protogine is, ac(>ording to Lotti. a talcose gneiss. § 1'-]. The resemblance of these rocks io those as.sociated with similar serpentines on the neighboring island of Elba is declared by Ijotti to be very close. There also the st>r- pentinic horizon is underlaid l)y gneisses and mica-schis+s, as in Corsica. Hi; concludes with Grastaldi that the great crystalliiu> zone of the Alps is connected through the Mari- time and Ligurian Alps with the similar rocks of Corsica and Elba. Kesting upon the opliioliti<' strata in Elba are found, accordiinr to Lotti, paleozoic carboiuiceous slates <'on- tainina- Or/hoceras. Oinlio/d. Arlinorrinu^, and probably also y-raptolites. Lotti, however, while he asserts the great antiquity of all oftlie serpentines of Corsica, and part of those of Elba, maintains th(> existence in th(> latter island of other serpentines which, like those of Tus- cany, he refers to the eocene period. A similar qtiestion is raised with regard to the granites of the two islands. Thus Pareto, who regarded as ancient, or at any rati^ pre-triassi(\ tln^ granites of Corsica, admit- ted for the granites of Ell )a. Monte Cristo and (ria'lio a i)ost-eocene age, a view which is also sustained by Lotti, while de Stefani, on the other hand, assigns the Elban granites to pre-triassi(^ time. I can scarcelv donlit that all of these granites, as well as the ophiolites both of the various islands and the mainland, will l»e found, as maintained by (rastaldi, of pre-paleozoic. age. § 74. If we turn to the island of Sardinia we find i' series of pre-Cambrian crystalliiu^ schists, said to <'onsist, in their ui>per portions, of argillites. sometimes talcose, sandstones, crvstalline limestones and dolomites. These, v.liich are referred by IJorneinann to the lluronian or pietre-verdi zone of tlie Alps, arc dverlaid. as was lirst shown by de la Mar- mora, bv a .series of uncrystalline limestones, shales and sandstones, containing an alnin- dant lower paleozoic fauna.* Of this, the Upper Cambrian (Ordovician) f forms were long since described by Meneiiliini. The subse(|ueiit studii's of Rorneniaiin. in 181^0, showed at the base of the series a zone marked by Pi(riii/(i.n'f/rs. ('(i/tdif/ihu/i/i's. Arclirori/dlliiis, etc., which have also been examined bv Meneghini. and establish thi' existence of a Lower Cambrian * iMiniciiiaiiii, snr Ics ^llrMlatillll^^ < <'(iiilrai'ti''l to ( inlnvian, waf- pnip..M'il liy l.apwnrtli In \>^'',\ ((iiii!ni)iciil M(iilii:iiii , \\.. |i. 11!,) tn ilrsi'_'iiali' tin' ;-'iniip(ir paK'.iZuii- rmUs (ihmuI in W'alrs lii'lwci'n llm liasc. of the. Tiowcr l.lan'lovcry ainl tlii^ liaw', (jf tlu' Lnwcr .Vrcniu'. 'I'licsi', (■nrn'spf)nilinj.' r.'<>cnlialiy I" tli(' I'ppcr ( 'amliriaii nr liala L'l'iiiip lit' Si' I'.'wick— tlic s(M'()nil fauna nf liarranilr— were, a.s i> well-known, hy a mistake in sti'ati^-'rapliy.jdinc.ci by Mill' liisnn 111 Ills Silurian .'^ystcin, umlcr the. nnnic ol' Lnwnr .'Silurian, ami have also since Inmn calloil Silnro-Cani- lirian ami t aiiilini-Siliii'ian. Hy niakiiiL' nf tliis dcliali'il jinninil a supnrnte r(';.'icin, iK^twiH'.n tlll^ trno Silurian altovo anil till' L'lcal ('anilirian ^erirs licluw. illic MiiliUe ami i.owcr < 'ainlirian nf Svl^rwiekl l.apwortli ha.s sonjiiit t(i ;.'('t rill of this iionl'iisiiiii in nonn'nclatnrc, ai'd to restrain the atteinpt.s of .some to nxtenil the name, of Silnrian ilown- wariU even to the lia.se oftlie f'aiiilirian itself 'I'hi.s ilesi.jnation is eonvenient in .\nieriean tie'ilo^ry from the fact that it imliiiles tlie ■.'I'liiip of strata hetueeii the liase of the Silurian i Meilina) sainlstoiie and the liase of the ( 'ha/y liliiestiille ; the, latter, tn'.'etlier witli !'ie 'I'rellton, I'tiea and I.oraine di\ isions, iH'inir eiillivalellt 111 t!:'.' Ordovieian. The nail' • is i^iven in aUtisioii to the Onloviw'S, an ancient lirilish trilo inhahilin^r North Wales. GKOLOGICAL HISTORY OF SEEPI^NTIXI-S. 193 lu.ishLb oi lead, silver and ziuc-ores. § 15 ^Yo huvo now .shown that tho.s.. rryshillin.. ro.ks whi..},. in ports of the mainhnd aro directly succeodod by tertiary sediments, are in dUierent areas ov ^^dlj v^Zs^' disproMno the views ot the older geologists who assigned to these same crvstalline n,eks a paleozoi.. or a mesozoi. age. It is instriLtive ,o ina;k the stops by wW h ^t^w has, xn he progress of investigation, be.n l..ft behind. In Xeri's seeti n t^^.^^!LI"i^ h pietro verdi proper are oalled axoi- or protoxoio, but the recent gneiss t^^ huvd to be paleozoi. Lory, howc..r, im.luded the latter in the primitiv' .series bu clWd he lustrous s..hists as altered tri... while huer, Claslaldi, and with him Favre, Xed ev n these in the paleozoic, until at last we lind Gastaldi adopting the conclusion rfr^putfo" § 70. The story of the ..rystalline marbles of Carrara, now included in this series is no I..S nistructive. They were regarded as eruptive by Savi. who taught that c^Z^t and limestones had b..n poured out in a lused state, alike lu secondary and in "d^ nnes, * and even indicated what he .supposed to be centres of eruption. The marl,les o^' ( ari-nra^with their associated schists, have since been called cretaceous. liassic, rhaetic infra- . ;.rbonif;M.>us and pre-paleoxoic. f They were in 1874, in the second part of Gastaldi's .^nulu, in.-luded in the rocks of the pietre-verdi zone, the term being then used in its Lr^^er souse, a_s embracing not only the true pietre verdi, but the whole crystalline series above tlie ancient gneiss. § 11. This was^ also clearly stated by Jervis, in his elaborate work on the mineral icsourcvs o Italy t a veritable treasury of informal ion. most .arefullv and svstematicallv arranged, In h.s lirst volume, in a trbular view of the gcoloo-yof the Alps, he hadalreadv adopted the views of (lastaldi, and placed the whole of ,lu. crvstalline stratified rockl above he ancient gneisses in a pre-palcozoi,- gronp, whi,h he n-garded as svnonvmous will, the pietrc-verdi zone. lu his se.ond volume, in a si.uilar tabular view of the g^oloffv ol the Apennines and the adjacent islands he further insists upon the same viX and puts above th." am'ient gn.'iss. in what he , ails the ]nv-paleozoic period, the great series of "stratified azoic rocks," in.-luding not only the ophiolite.s, and the rcent gneisses and other erystalline schists, but fh.> saccharoidal and ronipad marl)Ies of th ■ Apuan Alps (loc. eit 1' !'.) It is to be remarked, as shown both by Jervis and(^astaldi, that this great vouim-er crystalline seri.>s is the metalliferous zone of Italy, containing murh cupriferous and nicco- hiorous pyrites, in veins and intersiratihed bds, fog..ther with crvstalline iron-ores lead zinc and gold. " > > 11^ ^^''*'' *'"' =^'''»''''il ^U'vession of the Alpine rocks alivady giv.Mi, we may compare * Hniie. G.ii.l.ulu p'..leu'iM< voya-our, II., Lis. F„, ,|,„ virus „foiluTs as to ,lio cTuptivo erinin of orT«^> IlliirMelies, sel(,t.'ical Essays, p. L'lS. t l',M .1 uotir,, „fseni„ „!• ihn vi.rions vioxvs wl,i.-li linvc hcvu pul loiuanl »iih ivganl to tlm ago of thoso iimrlilcs, SCO l.<«li,,iii- 111 (ll(^ r,', „/„,;,■,.„/ .V„,;„:,-,„ fur ls7i!, lip, L'S7 ami ;;,s;;. 4 I ToMori !joltcraiioi dol'ltiiliii, 3 vols. 8vo, Turin, ISTS-lssi. Sc^c, IV., 1S83. LT) 194 DR. THOMAS STi-ERY HUNT ON TllK tho observations of Taramelli in tho Vallollino, whore he describes the ophiolitos as lying below a great ^-neissic and granitic series, from which they are separated ])y a garnetiferons hornbleudie rock and sat'charoidal limestones. The lowest division in the series, as observed in the Yaltelline is, according lo Taramelli, a quartzose tah--schist, upon which reposes the serpentine in heavy continuous beds, having all the appearance of a stratified rock, followed by potstone, that is to say steatite or chlorite. To this succeed in ascend- ing order, hornblendic and epidotic rocks, associated with crystalline limestones, often talci- ferous; then, schistose amphibolite, taleose gnei.ss. talc-schists and ech)gite, and linally a coarsely crystalline glandiilar gneiss, itself overlaid by granitic and associated hornblen- dic rocks. This apparent reversal of the succession as delined by Gastaldi and others, suggests the probability that we nniy have in the Yaltelline an overturn of the strata, su.di as is well-known in many parts of Die Alps, and elsewhere. pla<'ing the more ancient rocks above the younger ones. * § TO. It is here the place to notice tlie mode of occurrence of the serpentines which, in Saxony, are found interstratilied in the 'iruiiulite .series of the Mittolgebirge. Tho granulite proper mav 1)e described as a rine-u-rain(>d irray laminated binary gneiss, consisting essen- tially or orthoclase and (piart/, l)ut often arnet and sometimes cyanite and andalusite. By an admixtnr.- of mica, it passes, throudi ordinary gneiss, into mica- schists, Avhich are aliundant in the series. In it are also inter.stratiiied diclroite-gneiss, sometimes in lireat beds, and a liieeiiish hornl)lendi«' gneiss, as well as the so-called gab- bros of the reij-ion (like thai of Neurode.) These occur in laru-er or smaller lenticular inter- stratilied masses, to which the distriliution of llie diallage in a granular labradorite base given a well-defined giieis.soid structure. In this same series the serpentine is found in interstratilied l).'ds, occasionally garnet iferous. and sometimes associated with Iherzolite. \^ so. I have not seen tliese rocks on tli(> ground, but have examined a large collection of them in Leipzisr, with tlie assistance of my friend. Dr. Hermann Crediier, and wasstriick with their clo.se reseml)lances lo the rocks with which 1 am lamiliar in the newer or ]\[on- talban series of ii'iieisses and mica-schists throuu'liout tlie Atlantic belt (jf North America. Tlic mii.scovite-oneisses of the I'lrzuvbirue, willi tlieir occasional layers of limestone and orhornl>leii(lr-v(),k. and ilieir intercalated and overlying mici;-.scliists, I also refer to the same general liorizou. It is in these, il trill be remembered, that are found the ahundant conulomeraic l)eds dcsrribed bv Saner, the pel)!)les in which consist chielly of varieties of Li'ranitoid u'liciss. resemlilini^- on- domerates in Swed*Mi. at Si^ljiiariie, wlier.- pcht.j.s of aii' ieiit -'iieiss and i;T;iiiite are loiind at several poiuis iiuUMhliMJ in liiie-LiTaiiied srhi.-tose gneiss, in calcareous mica-schist, and al.-o ill a red hallellinta, the sinita of all of which are shown to rest unconforinably upon the older t:'raniloid giici.^s. .J: * lioll. Soc. Gwil.v_'lfa Ttaliana, T., \x 14. •!■ Zfitx-lirifl f. (1. '-'.'s. N'aturwi-^. P.ainl lii. ; alv. ( i.'ol. Ma-. .Ian. l^s^', ,ni.l I'.iill. S,.c. ( irnl, ,1c, Vr.. n. LV,; nl.-^o .\iiicr. .I.piii'. S. ii'iicc, i!'. I NX\ i.. p. I'i7. ;. lluu.iuci, niuSvcri^'cs l,;igrado riljciy.,ctc.,StiM'lihi)liu, IsT.J, (I. ;;". GEOLOrrTC'AL IITSTOTJV OF SKTJPI^XTFNF.S. 195 § 81. Tt will bo romomborocl 1)y studonts in geology that in IStO tho present writer announcod his conclusion that there exists in North Ameri<-a, 1)esi(le.s the Laurentiun gneisses, "a great series ol crystalline schisis, including mica-schists, staiirolite and chias- tolite-schists, with quartzoso and hornWcndic rocks, and sonic limestones, the whole asso- ciated with great masses of fmo-grained gneisses, the sc -ailed unuiites of many parts of New ICnu'land." * Tliese rocks \ver(> especially indicated as occurring in the White Moun- tains of New Hampshire, but were also said to he found to the northw^est of Lake Superior, as well as in Ontario and in Newfoundland, in whidi last two regions they w^en; believed to r(>st unconformably upon tho Laurentiau gneiss. In hotli of these latter localities, there were provisionally associated with this group some hiiilicr limestones, with crystalline schists, and for the wliole series the name of Terranovan was suti'gested. § 82. In the following year, 1871, in an address hefon,' the American Association for the Advancement of Science, these rocks were farther noticed under thi-name of tlie "White j\Iou)itain series. The higher limestones and schists, a\ liich were not found on the geolo- gical section then described, were however excluded. This great series of younger ii'iieisses and mica-schists was then assigned to a horizon abovi> th(^ Huronian, and as a distinctive name was desirable for a seri(\s so conspicuous in American geology, that of Montalban (from the latinized name of the "White Mountains) was proposed in the same year, f It was at the same time shown that the view held by most American geologists, that thesi> rocks were altered paleozoii- strata was untenable, and that they were to be regarded as [)re-paleozoic. At a later period, the overlying limestones and schists, at first associated with these newer gneisses and mica-schists, were refered to the Lower Taconic ofEiiimons — the Taconian series, (f) When, in 1870 and 1871, I thus attempted to subdivide the crystalline schists above the ancient ti'niMss of North America, and to deliiie, above the Huronian. a younger series of gneisses with mica-schists, I was not aware that Voii llauer had alivady been led by his studies to similar conclusions for the Eastern Alps, and had discovered above the great pietre-verdi zone, a series of gneisses with micaceous schists, as indicated in divisions 5 and (1 of his section {^ M). Gastaldi, in 1871, and for years after, included the.se, with all the ( rystalline schists found above the ancient or central gneiss, in one great group of newer schists, which he assimilated to the Huronian. In reviewing this subject, in 1878, t I liointed out iliat tlie uppermost crystalline schists of die AVesiern Alps should !.• separated fnuii the Huronian, and compared them with the Taconian, while I noted the fact "that gneisses and mica-schists similar to those of the Montalban are found in many parts of the Ali)s."' It was not, however, until after iny studies among these rocks in 1881, that I referred the newer gneissic series of that reu-ion to the ilontalban, for the two-fold reason Ihal it ocI, Her, L'."), isTl, |). IL'SS, uiul A/.nic Kii.ks, p. ISl. X Azoio liock.s, pp. L'Ol-L'll, lilo ; X Ibid, i^. I'lo. 1':-siy<, pp. l!U, ill, 2S'J; Das Auslaiul, 196 i>R. TiroMAs ,sTi:ni!V iruxT on tiik i: ordi^r. a(vov(liiiir to Giimbcl, first, iho rod or varicgaiod trnoiss. callod by him T?ojian. -which is toUowt'd imim>diiUcly l>y tlic iitnvcr yrcv or llfrcviiiaii liin'iss. his second division, and by a third, tho Hcrcynian inica-sciiist scries, oicasioiudlv liornhlcndic. To this siicrccds in the fbnrth place, the Ilercynian primitive clay-shite series, which is immediatelv overlaid bv Ijower Cambrian fbssilif ('r(m.s rocks. Tin s primitive clav-s lat. series contain.s inter- stratilied beds of limestoii(\ sometimes dolomitic. attaiiiiiiL;' in i)laics a tliickiiess oi' i\'>() leet. and associated witli siderite. wiiich 'jives vise by c[)iy'eiiesis to valuable dei)osits oi'limoniti' along itsontcrop. Witii these limestones arc (bund varieties ot hornblende and serpeiitino, accompany iiiii- which is the I-aizooh lldniriruin ol' Giimbel. s^ S4. The Ilercynian gneiss is described by Giimbel as including much grey quartzo.se and micaceous u'ueiss, with ii.>quent beds of dichroite-i'-neiss. granulite, .serpentine, horn- b](Mulie schists and crystalline limestones. "With these are a.ssociated Lozoon Cd/Kir/cnsc. Irom which Giimbel supposed tliis upper jjiieissic series to represent the Laureutian. a view which was accepted by the present writer wlicii. in istitl. he translated and edited (Jiim- sel s paper * for the Cnnniliini Naliinilixl. and has since been expressed by him elsewhere ; coupled with the suggestion that the I'ojian miulit correspcmd to the Ottawa gneiss which underlies the Grenville series, the typical Laureutian (Lower Laurent iaii) of the Canadian survey. We are not, however, as yet prepared to recoi>-nizi' a sub-divi.sion in the older gneis.ses of conti: ental I'hirope. and meanwhile the analoo-i,.s between the y-reat Hercyuian gneiss and mica-schist series combined, and the younger ■••neis.ses and mica-schists of .Saxony and of the Alps, lead us to refer what Giimbel has described as th.' newer gneiss seriivs of Eodenmais and the Danube, to the sain.' horizon as the younger gneisses of Gas- taldi and Von Hauer, the Montalban .series : wlii.ii in eastern liavaria would seem, as in the Simplon, to rest directly upon the older gneiss, the Iluronian being absent. The Ilercy- nian day- late series, with its crystalline limestones, may ('orresix.nd to the iburth group of the Alpine rocks, the argillo-talcose schists, which we have compared with the American Taconian. IV, — The !ciise as emlnarJMu' all the newer crystalline rocks, or those al)ove the ancient li-iieiss. In b^71. in ih.^ Ilrsi |.art of liis mria,,ir .,11 the Western Alp.s. he declared it as his opinion that "all the .s,.ip,.i,ti,uc mas.ses of the Tu.scan and Liuurian Apeiiiiiiie., and the .serpentines, ophicalcites. .sa.vharoidal limestones and -raiiites of CalalH'ia, are but a prolongation of this zone." In this w.tc in. hided, as we have already seen, the Apuaii .\ii)s, and. farther westward, a lar-e i)art of tlie Maritime Alps, In sup- port of these views he poinl.'d out the luiueraloni.al idculiiyof llu- oi)liiolites and otlier crystalline rocks in the .Alps and the Apeiiniiu's. To th,. .ch(M-. fi-..'elMiw, ^riiiirhcn Aka.l, SJJtznn.'O. Is1.l1. 'I,j pp. L'.VTii; iits.i Cjui, Natnr:ili.«t, iii., isiis, i,),. sl-Kii. CJEOLOOICAL IirSTOTlV OF skrpi-:ntines. 197 nnd oal.-aroous ro.-ks, opposing loss rosistan... havo W.n r.mo\ .d l,y d.vay and erosion adducing many instan.-os in sopport ol' this among tho Alps. This hoingthe case, he adds we are not to be surprised when in the Apennines wo find an isohited masses of ophiolite rLs.ng out of the midst of surrounding. jurassie, ere.Sireous or tertiarv strata, whi.'h eon.-eal the rocks that a.Torapany the ophiolite. Thus it is. he a.hls. that " the notion has arisen in tho Apomnnos that the s.-rpentines, diorites, etc. aiv alwavs erupt ive rocks." They are in his view, to make use of the happy ."xpression of lioland Irving in describin-^ a similar ocurrenco, "protruding but not extruded." These views were r.'iterate.l bv Uastaldi in his letter to Zezi in IH?.;, when he asserted that the skeleton of the Apennines is a .'onti- nuation of that of the Alps, and that the crystalline ,o,ks of the Apennines are Alpine rocks. From the summit of Mont Blanc he declared, thev mav be followed, more or less conc..aled by overlying strata of more r.-cent date, * to the Danube, to the plains ofFram-e to th.. Mediterranean, and along th.- peninsula which separates this sea, from the Adriatic • assertions whi.-h ho supported in 187S by many detailed observations to be noticed far^ ther on. § 87. These bold uvneralizations of Uastaldi have met with l)ut partial acceptan.-e in Italy, as may l)e seen by the dis.iissions in Issl. and the publi.ations of the 1{. Comitato (loologi.-o and the Hocieta Oeologi.'a Italiana in Issl and issi'. already referred to in § 43. r.dlati, in his summary, declares that th(! views of Uastaldi" as to the anti- quity of the Alpine pietre verdi are confirmed by the work of Haretti and of Taramelli, the latt.T of whom .'learly shows that the view entertained l)y so many that these rocks are .•arboniferous or triassic, is inadmissible. Hence these ancient serpent in.-s are by T.-llati designated as pre-paleozoi.- (eozoic) This view lu- extends to all the ophiolitic masses situated in tho Alps, lo those of Calabria, and also to tliose of th.' Apennines west of the meridian of Oenoa, those to the cast of this meridian being included in the eocene. §47. § 88. Regarding the so-calh'd eocene s.Tpeiitine, and its associated rocks. Fellati observes, "as to its I'oinposition, it dilTers but little fr(nu the older serpentine, the differences remarked being principally in a structure ordinarily less schistose, and in a greater fre- quency of subordinate ophiolitic rocks : euphotides. euvites. diorites. variolites. ophiooal- cites, etc, more or less decomposed. Tlie masses of proper serpentine are ordinarily more scattered and of smaller dimensions, having almost always gal)l)ros and l)eds of phthanite and jasper around them." Cossa, it is true, has remarked in the >perimeiis examined by him tha* the mineral spi'ci.'s bustite i.s nion^ common in t lie eocene m- .\pennine than in the eozoic or Alpine serpentines, but. with tliis possible exception, the mineraloo-ieal and litholouical associations of the two are apparently identical. In fact, rdlati admits that it is in .some cases di'.liiult, if not imi)ossil)le, to distiiiu'uish between them. Within the great basin lyinn' to the east of the meridian of (renoa. and einbraeinu', as we have seen, the so- called tertiary serpentines, we are inlurmed ])y liim tluit ' the psije ozoie and mesozoic rocks are generally very thin, and ol'ti'U are entirely absent, in which case tlie floor i)[^ pirfrr rrrdi or greenstones is directly overlaid l)y t!ie tertiary, and in fact l)y the very eocene which includes the younger serpentines. This is the case in the vicinity of (lenoa, upon theriu'ht bank of the Poh'overa, where the greenstones come in direct contact with the shales and the limestones of the upper eocene, and it hen' i)i'comes doubtful whether, along I liis line * bk'ii tlm iiiither cm .Vzeic Ko( ks, p. 'J-1.'). 198 Tin. TUO^[AH STEETJY TITNT ON TIIK of oniiTop. portions of 1(M'fiary ophiolit(is nro not mix«Hl iiiid ronfonndtHl ■vvilli othors of the l)Vi'-|):ili'ozoi(' period. '" Tliosc supposed li'itiiivv oiiliiolilcs ■lunc a vory livoiii ri'scnibliuico lo tliosc of the eocene of eastern Lit^uria. and ]^resent moreover a hirji'e development of of the roeks which Tssel has designated as amphimorpliii' {§ Hii.) Thns. near I'ietra Lavezzara. lor example, ophiealeites are exploited Avhieh are precisely like the gTeeii marbles of Levanto. Tn tliis siuue locality, moreover ar;.;illites, liavi'im' the aspect of those of the oooeuo appear to dij) heneatli the ophioliles." In su])port of tlie belief that those seemingly tertiary ophiolites are really eozoic. however, we are told that tlnir ontcrojis present lines of '(tnlinnity. connectinu' lhes<» serix'ntines with those of which the eozoic oritiin is iindoubled. AVe have set>n {^ 41) that I'rof. r>i)nney in his studies of ih(> serjien- tines of Italy fails to remark any distinction between llie serpentines thns .separated by the Italian ueoloiiists. since he describes as sinuiar boih in mineralogical characters and in geommstical relalions. the opiiiolites lyinn' to the west and those lying to tln^ twsi of the mt>ridian of Genoa. I shall further on liave (Kcasinii to refer lo my own obser\ation.s of some of lliese localities. \^ S'.t. The older school of Italian yeolou-ists. as alreadv noiieod. sui)posed the serpen- tine> to liave ])eeu erupted, like basalts, at dilferent i^'colouical periods, and applied this vicniines. Tellati remarks that t lie recent studies of Italian li'colou'ists liavc led id hypotheses wiiich ditli'r widciv from ihuse formerlv received, acordinL'- to wiiich seri>i'ni inc^ were reiiarded " as plutonic or erui)tiv»', haviiin' come to I he sui'lace iifier the maiiiier of volcanic lava-, or at least, like certain massive trachvtes. in a pasty slate, oi' (.lie of iuncoiis semj-llnidity," ( la-taldi. I'c add>. " from his studies of the ancient Nerpeiilincs of the Alp.-. iVLfaidcd thcin, however, as sedinn'iilarv rocks, modi- iied hy -uKsiMjiieni liydroihermal actions operatini.;' at ureal di'plhs in the earth." IIo cdinpaivd their formation to tliat of the acconipanyin^- liiicisses. mica-schists, chlorite- schists, cryMalliiie liun'st.ines. (|i(,riti's. ande\cii the uraniles, syeiiiteis and porpiiyriew of till' .\lp.-. Ill all of which !ie iiscribi'(l an iKpiedus oriiiin. \^ '.'1. This hypothesis has md. ho\\c\er. been favorably iv(ei\e(| a> an explanation of the oriuin of the so-called tertiary ophiolile> ,,f the Tuscan and Liu'iirian .\pennines. Tara- inc'li; lit. Ill !ii,- studies of the serpi'iitiiii's of the valley o|' I he Trcbliia. declared that neilher the abii\e ill. nil iiied view n|' ihcir iiiiieiiiis erii|itive oriLi'in, nor tint maintained hy (ias- taldi ci.iil.l !„■ conciliated with ihe laci> ,,f th,. stratilorm and leninular arrangement of I he nlasse^ of ber]jeniinc. the want of evidences of alti'ratii.ii in th.. iiilcrstrul died layers of - liiae.stoiK's and argillites.and the ahseinv of opliiolitic dykes in the.se sa,me rocks. Jle was GEOLOGIf'AL IIISTOF!Y OF SERPHNTINES. 199 thus led to eoueludo that tho ophiolitos had h.vu Ibrm-d in the inidst ol' tho t.rtiary sedi- rr? ^7^;""*^7';7--V-^|>'---i- -•upt.ons or .u.,n,.sia„ and IHdspathi.. magmas, .Hid that tho euphot.dos and .Xhov associatvd nphioHH,. nvks had probablv resulted from sul,sequeu( erptalloovni,- ..oun.nl rations, whi.-l, took pLuv in these ..rupted ma-mas Capae..,, Irom Jus mvesti^atinn of the ophiditie mass of Mo.itelerrato, in Pruto, advam'ed a snudar view.supph.meuted hy the hypothesis of .hormal waters aeeompanvino- the erup- tion ot the mau'uesian niau'uia or succimIIiil. it. § !>± Iss.l and Maz/uoli, IVoni th.ir Joint studies in eastern Lio.ivia, liave formuhited more at h-ni-lh. an analon,,„s hypothesis to ..xph.in alik. th. oriuin of ,he s.rpeutines and of the roeks there intimately assoeiated with them, sudi as diorites. aphanites variulites and ouphotides. To these, they uive the .vneral desin.nation of amphim.>rphie roelc su- gosted by tho eonoeption that they have had a two-fold origin, and have resulted from mix- tures and oombinat ions of slowly depo.Mi.d ar-illar^ous matorials of moohanieal ori-in with elem.Mits brou-ht ,n by abundant thermal sprin-s tlin.uuh a lonu' porio.l. boih duriu.- and alter the eruption of lhe,serp,.nlinous mao-ina. This latter, th.v suppose, was a phenomeuou ot short duration, almost instantaneous, whif- the f.rmalion ..f ihe .uphotides and other amphimorphieroekswasa slow pr..,vss. \or is this th, o„lv ,.|lirt ascribed to the hypothe- tieal th.«rmal sprinos, whhh onr authors suppose to have an,.,! „pnn pre-existin-- e.mti-uous '".leareous and ai-illa..eous strata, peiiotratinu' them with waters holding in solution siliea aud oxyds ol iron and man-an,.se, ami eonverting thein tojaspers. phthanites or silieious slates, or to <-erlain ill-.l,.iine.l siliro-argiUaeeous or ealeareous roeks whieh Issol has ealled hyi)oi)hthanites. i^ ;>;3. The serpentines themselves havin- iioiliinu' in ruuuuon with the arouHites. sand- stones and llmestou.'s am.nig whirh tlieyare fonnd. these observers have imagim-d that alter the deposition of the eoeene sandstone, -reat eruptions of a hot impalpable mud, eonsistin- primipaliy of siliral.s ofniaunosia and in,n. ne„,.vab.d bv some unexplained pro- cess, won. p,,nrod out from submarine iissun- j,, tl, .iifs .■nisi, were spread over the bott.nn of the sea. liijing depressions thnvin, and wore sub.se.juentlv .han-ed into serpentine. Thus, by this hypothesis. •■ (he .serp-nliues are eonsidered as oruptiw with.mt being truly iuneous. inasmieh as i hey do not roulain iiM heir eompo.sition any mineral ^^ ''■'■'' ^'"'^ ' " ■^Hl)niitlo,l to iuiiooiis fusion, and -jo n,,i sliow. at th.-ir eonta.'t with th.' sediments adjoiniiui', any m.^taniorpiiir luodu t duo to a wry olovatod tomporaluro. hi order, however, to explain tiio sliu'lit tra.vs ,,f o,)iitaot-metamorpiiisin wliioh are e,sp,vially seen in eiielosed mas.scs of linieston,.s. tiioy admit that at the moment of its emission the mauuia may liave had a touiju'rat iiro of si^voral hundred doo-r,.,.s. .\s to the ()|iluoaloitos. whirh aro nft,.ii found at tie^ ,| essi'iitially of rooks of the same nature and the same ooniposilion." ilejnsists iiK.ivover upon farther resoarehes, even iii the ease of the supposed eoeene ser- 1 200 DR. THOMAS STEI{RY HUNT ON THE i pontiuos, aiid upon the importano(^ of discovorintr the reutros of eruption through the pre- oxistiiig strata, " or at least souio i>nsitivo ovidonrps of such contros." § li"). I have thought it desirable lo reproduce with some detail this ingenious hypo- thesis, with Pellati's comments thereon, lor the reason that it shows clearly the dilRculties which recent observers have found in accepting the older theory of the igneous eruption of ophidlites, and moreover brinu's clearly into view many points which are of importance for the solution of the problem before us, of t lie true relations of these ophiolites to the surrounding strata. In view of the fact that theresemldance l)etween the supposcnl eocenic and llie eozoic ophiolites is so strong that the two cannot be clearly distinguished or separ- ated from one another, as we have seen alike from the comparisons of Bonnev and the admissions of the rec(Mit Italian li'coloii'ists themselves {§ 88), it is not sur'n-isiiiG: that some observers like Cnistaldi should have been led to look upon the so-called eocene ophiolites as nothing more than portions of the underlying eozoic or pre-paleozoic series exposed through geological accidents. This explanation bei'omes more plausible when we reflect that within the great basin over which these ophiolites are met with, the paIeozoi(> and mesozoic rocks have but a slight development, and are often entirely wantinany. It was my good foriune in October, 1881, to spend a day with Siunor Capacci. (whose rai'eful nuMnoir on tln^ region, with map and s(>i'tions, I have already noticed,) in going over Monteterrato in Prato, near Florenci>, a locality for cen- tnvi(>s famous for its quarries of serpentine, known as rrrifr-/)r(ifo. About three miles from Prato. a town on the railway })etween Florence and Pistoia, is thi> little village of Fiu'line, wliicli lies on llie eastern slope of the ophiolitic mass in (luestion. forming a hill which rises Itoldly from the plain of eo.'i'ue limestones and shales (albercse and u'alestro.) The mass of ophiolitie rocks occupies an area somewhat oval in form, havinu', accordinii' to the detcr- iiiiiiations of Caparei. a li'iiiith of aJKiut 2,(500 meters from north to south and a maximum breadth of about l.SOO meters. In its highest points it attains elevations of 400 and 42(! meters above the sea, the level of the surroundiim- plain beinu" about 70 meters. Fii>line itself where the seri)eiitine appears from ]»encalli the eocene .strata lyiny- to the east, is at ale\,.l,,t' lo:! meters, but thi' similar strata on the western side of the hill, where they apparently dip at hiy'h angles b;'ne;u!i the seri),'ntine-mass, rise to heights of 2!1.') aiid ;{22 meters al)0vc the sea level. \^ '.IT. rnderlvina- tiie alberes... mnl restiim- upon the opliiolite along the eastern base of the liill. is sei'n in many |)lners a line-i>Tained, laminated silicious rock, geni«rally red- dish, but sometimes greenisli or |,o,*it8 ari« foim,! alilto at various Imrizuiis ii, tli(^ n|.iHT h..i(mic., aii'l in .'rota mis aiM iiaMsl,> strnlii, -iftiMi iiitliin lnv,,K.rieh, Ira.lin^' the anther to .„nchi.lo with lie stt UiMi that tlu'V am ih)oj(-»na ilipnf-il*. GEOLOarOAL IirST ,]^Y OF SKKPENTrNES. 201 of eocene limestones and shales w1,ir1, ;, , ophi„li„, „, „i„, the intcrvo„li„;, onl y ^ l.Z° f °"'' TT' """ ''""">' »'"'■' ""e
    away from the .s„rpnr.li,„. that is lo ,wl 7 , °""'-""* """'" ■■"« " "«°«»1 ..oariyh„ri.„„eal. with ™aH um.uh , u ;: iii^:': J^l "' .^^r"''^ ^'■""°"' »^ Borponliuo bonoath tlio the o]bor..,o ° '^ ' ""^ Pl"""™"^. «ndoye.i tho »>uthw,.t border. i» ,V„,„ .W ,' ."To ^i «,;'"; f' '^T"' '""•," ''■'-' "'°"' "^» whi.h i, »how„ iu tho ,o,.|i„„„ of Capa,. i ■ ™ Xth i^ " i'"* " "*■'"■"'"'" '"■='• .ho sorpeutino, phtha„i,o anclalborose a ;X:,Nv in tT"°": '■■''?'' "'^ roolis appear in the a.e,.i,.ii or,l ,, ■ . " "', " '"'" "" "'" »»stern slope these three .ho phthanite, and the " t,: ,. e"" .i;;:':';'™;''';- ^ ^ ""' ^"^•'"""" °->^»« facts is that wo have here .ira,,! • , ' , ^ '"""'•''"""'"'""■'"< """P'^.alion of these overturnof the strata on ;,.::::'■;;;'»;;;: :;;™h;,;'>° '■""""' "■■""■■' --w"^ f- - vJ;;i:tw:;;;::':^r:n:r2^!zt;^^^ jo^ewhat ea.„reons d.ori.ie roe. e retionary i!:::::,:: ^^zz::!;-:^:! Tf 1 , a,v„r,lan.H. wit]i th,. hvp„|l„.si.s alivady sot forth (i ^^) ":st::zr'':;::,rrr;:.ir: \' 'i--:':--C'.^» strata of alht.r.v. '»f"'"i''' ' "i poiloct ronmrdan.v ,.1 stratilifatimi, amon- tho t iT^ si " ;V ; r r, "■ '"'■"■" *-•-"-"-" wln-h ha., boon subsoq,;utlv ^r;Z^^''^'\ ''"T T'"" '"' '""•-"^ "-" -"• -'I -as subsotiuonUv ovorki.l by 1 •oloro. lii'sili.'iouss(Mliinciit(oiisii(uliiio-th,, phtha- '■it-"whi,. onthowosi suhMs s,vM I,. ,.n.I..,li,.,h„ .,.1. .li.o is, i„ , his viow, a portion ZT • 'T'"'r' ""'■••'"^ ^•-'- -•"■''• "- .'•-l-u.o o„ ,ho oas. sido ;s LtlJ I'oition of a sun.h.r so.lnnoMt. .subso,ju,,„ly lai.l .hnvn upon il,o ophioliio §101. Ih, ophioliti.. n.asH is thus, liko all ,bo olhor s.Mpo„ti,uvs of Tusfauv. ofoooono ; mso! i 'VrT ^V''"'' '""'"■ ""•" "^ """"""" '"''"""■ "^ ^'- '-"^ of "lo„,iouh.r .ass o, annm.lshapod u.n.vu.rations," of ^vI,i,■lMho ..uphotido and ,ho ^abbros are . nplos. I h. .abbro-rosso is Ibun.l in nmssos a, .ho ooulaot of .ho ophiolilo with tho '-. Jhoso havo also ohanyvd tho jralosfro in.o tho i.hthauito found both abovo and Soc, I\'., 18S3. I'a, I 202 DR. THOMAS STERHY HUNT ON THE l>|i! I;!! below the ophiolitt^s. and in iKn-foct conformity witli th(> adjtvont oocoii(> strata, '■ whifh liavt' all their ilistinctivf charactfrs, aiid ])ri>s('nt no traces of alteration or of nielainor- phisni," "the action which prodnced the phtluuiitcis beiiiu' local, iiarticnlai-, and variabK'." Rocoinposed rooks, made \\\i of L;iaiiis and frau'iuents of f^erpi'nline. in a ( cmcnt generally ciUcareous. are found on the coniiiies of tlie .seri)entine and at its contact with tln^ phthanite. This is especially seen at To^'iiio, on tlie Koutheast side of the hill, where I found a veritable conglomerate of fragments of serpentine iud)edded in a paste of silicious slate. These facts, as well remarked by Capacei. show that jn-evious to the deposition of these eocene l)eds. the scrpcniiih'-niass alonu' tlie sjiores of a shallow sea, was subjected to a proci'ss of disintegration ; 'and lliat, moreover, llie formation of the seri)entiue (Mrresponds to a kiml of pause in llie deposition of tlie eocene strata." Tlie ophicalcites, iu liivc nuuiner. are lound at the limits of the serpentine, and are breicias or conglonu'rates with a calcareous cement. v^ 102. I have thus uiven. in ureal measxire in languau'e translated from Capacci's memoir, the principal facts ob.served at Monteferraio. which I have, for the most part, veriiied. They, however, appear to nu>. iinonsistant with tin- hyi)othesis propounded by the modern school i,f Italian ui'olou'ists, and with the eocene aue of the ophiolitic mass in question. The ell'usion of a li'reat nuiss of a(pie()us material from the earth's interior into the eocene sea, its suksecjuent arrangement and crystallization iuto luoui; tain-masses of eaphotide. diorite and serpentine, the elevation of the.s(>, and their subse(|uent disintegra- tion to form the ophiolitic sands and conu'lomerates already described, marks a u'eolouical period, and a revolution whi» "'rata dim.mg Mo„t»fe„,ao; tlu. .tn„a appt ,.:,,,. ^l^'f? '"r" "' '"!" «»'-■" '- »' fre,,.,.„My ,1... ,,„., ihi» in, nu.tio^; s» 1 ' ^ , , ' 'i ^ -'P'-f»'*'™- W'-"". - « syu.Iinal, Iho sain,. sH-ih will ,,„„.,. . ' "'""' "*' '" "" <>™-t"™e' """""'"'T' '° auc„d..i„ithau,o..tio,,ia,K>v,i,;,aiai:pu:;,::;,i: •^'■' "" °' ■"""■'""'• -^ ■""" S 105. rrof. Il„,n„.y who. aH w hav,. ,s,.,.,, h„|,lK |„ il„, i,„„.„„, „,,„;„ „( ^ ^^j .^ ,,,;';;;::':;'' T" "*";''°"" -^ ""• ""'"""•• ■^"'' ■"-» ■' -' "i'™" a' "t^- .1 .,. lMd,„,.wha| h,. r,.s,,r,l» a. a '■,„,„|,]H,. proof „f ,1„. „r„ptiv.. ..afuv of the »orp,.,„„„. pU.,„, .^,h,. ...trusiv,. ,.h,>r„W,.r or ,h.. ,,„„.r b,,-o„<, al do„ ":„ , , J ■ ^i,::; ■;: : LI™ ■""■ t '""" •" "'" -''■ '""''"''■■' '•>' '■"" -•-• «" '- "I ^,l,l„o) IS mini. >.. ,„ (h,. s,..p,.,„„„..-» \VI,al,.,-,.r vi,.w ,„„y |,„ held of the origin .M nl,,d l„.l„v„ the ,.ph,„lM„. Hia..> a,id Ihe he.ls of phlhanile, a„d ,.v,.„, a,. I oh.served ,,,. »,..,,..> alo„. ,h,. .o,„h,.a., has Ihe hill, the ,„ „e,. ot rra.,„e„i: of „.rp,.,;th,! (he eocene heds is untennhle. M0(!, The examinations whieh I liave heen able to make of the ophiolitie roeks of w7 -T'Tt""-^ .p,.n,. ,i„l,. ,i,....near 8eslri Levante. under the .uidan.e of ••<>l.(.. tzieliol lunn. was.snehas (o leave no doul.t in my mind th.t we have here as maintained hy (lastahli, portion, of an aneieni s,ra,i,i,.,l ..erls rising ont of the o^^ lymi^ .•oe.me, In addition to tin- vari..,ies of serpentine, and of ...photides. diorites, •liabases, (the amphunorphie roeks of Issei an.l Mazxnoli) we lindeurites. jaspers epidotie and steatit.e roekH. with oeeasic.nal li.neslones, and v,..rions ivpes of ar^•illit..s. ineludin- the hyp.>phthan.(es of these ,uithors. Thf whole series, inelndino- i,s masses of pyritej more or less eupr.ferous and nieeoliferons. pre.s-nls a elo,s„ resemhianee to theo-roupof strata a.e.ompany.ni.' the serpentine ofihe Unronian .seri.-s in Eastern Cannda, with whieh 1 hav,. l„nu' l,e,.n fan.iliar. These ro.ks are well .seen alon- the valley of the Aequa- ''••■'ol. MiiLiaziiie., AiiK'.,Isr',l, vel. vi., p. Wm 204 DE. THOMAS STEERY HUNT ON THE i; H f a, 11 observations at this point served to strengthen my eonvietion that ihe ophiolite of Monte- i'errato is also but a small i)rotruding mass oi' Ihe same series. I was enabled subsequently, as already noticed. (§ n4) to examine with Siguor Quin- tino Sella a portion of tht> ophiolitic series of admited eozoie age. as seen in the Biellese, in the i)rovin(e of Novara, and to eonlirm the judgments of Gastaldi, C'ossa, 15onney and others as to the ap[>arenl identity of these aneiml o])hiolites with those Ibund in Eastern Liguria. § 107. We have already di'scribed, in a former part of this paper, tin* mass of eozoie serpentine which, in Staten Island, New York, rises from out of the horizontal or gently iniliiicd cretaceons and triassie strata thai have bc(>n de])(isited around its base. If now we conceive this region to be subjected to such movements as tlio.se which, along the eozoie belt a little further south, have compressed the Primal and Auroral strata, against the northwest base of the Si)uth ]\Iounlain, and given them a southeast dip, we should liaA'e a phenomenon not unlike that presented by Monteferrato ; that is to say, a lenticular mass of ancient serpentine rising alouii' tli(> outciop of southeastward-dipping mesozoie rocks, anddiifering only by the accidental circunisiaiice lliat these, on the two sides, belong to dilferent mesozoic horizons {'22. "28.) VI. — The Genesis of Seupentines. ^ 1(18. As regards the origin of the serpentine-rocks, we have already noticed brieily some of the hypotheses which have been proposed. Although those which suppose it to !)(> derived by metasomatic changes from aluminoxis or cabareous rocks, either exotic or indigenous, such as granites, diaba.ses, granulites or limestones, may be considered as now nearly obsolete, it may not be amiss to recall the fact that they represent two distinct and op[>osite .schools, whi'']i agree only in admitting an unlimited alteration or change of substance in previously-formed rocks, through atpieous au'encies. The iirst view, which may be described as a li'eneral metasomatic hypothesis adapted to plutcnism, is that which derives not only serpentine but limestone from ordinary types of feldspathic rocks, such as granites, granulites. gneisses, diabases, and diorites. The integTal (diversion of all of these into serpentine by the complete elimination of the alumina, alkalii's and lime, aiid the replacement of th<>se bases by magnesia, has been mahitaiued by many writers of repule bcilonging to the school in question. * § ln!». Others still have supposed that the same rocks mie-ht 1h' chanu'cd into limestone, ]>y a complete removal of the silica, also, and the substitution of carbonate of lime. This extreme vie\v has found its boldest and most consistent advocates in Messrs. King and Kowney. who not diily assert this oritrin lor ihe limestone-masses i'otind in the gneisses of Sweden and the Hebrides, but imagine I hat ihe hedded iM'ystalline limestones, many * Mdiincy, wild mnintiiin.'* tiio on).'iii of .scriH.iiliiics by tlic hy'lnitidii ef cniptivd eliviiw-nicks, Iihs, in h'w paiK'i- :ilica.l\ . ii.«l, ;.'ivHii iiiiiiiy rcnsmi.K Inr ivjcliiiL' iIk, iidtidii ol'tlu^ fnrniiitieii el' stw'|ieiilhu's liy iiictas(iiniit(i.si,s '' ' ''"' '"'■•'i'' I'eM^'liiitliic iiirksso uflt'u a.-.snriatiMJ tlicnuvilh. The nliMirvod ri'latiiiiis of tliii two are, in lii.s iiliiniun, wlielly (,|,p(.>r.| le (liis vi<'\v. an. I lie. in.sist.s upon the. dilli.'nlty oCciniviviii'.' that .snrli a lim.v.ss ol'clianno shoiiM h,. liniiic.l lo.viiMMi imrtsorii ^ivat ma.xs, while leavinif mljaeent iKiHions uiialtoriMl. I'lum their .lintinct- ncs'<, hr ivcvcn leil to (lie rou.lnsion that thesfriKiiitini^N an.l tlirir ar.oiupanyin^' I'liiihoti.le.s and .liorites lKiI T No-th America nnrl l,n,r 1 / 1 ""''■'"'^"*^"^ "I *he Lanrentian j-neissic series of W ifi ; T "" *'''''^ "' .oniiuuous lines of outcrop lor hundreds of miles views of this school, an origin hy metasomatosis (or, as thev call it, m.^thylosis) from If serntl n f f''}''^''''''''': ^he existence of ophicalcites, the presence of masses so m V 1 17^ 'T'''"r ^^'•-•^— ^--" C.nad.., in limestone, are but 10 n"'"/^ ':•" °' ^' "^''" "--"1>1^^^-1 '"-version of serpentine into limestone, subs In ,^'^P'^f ^ ^" ^'r^' ^^^^^"^ "••"^"^>^ of serpentines and limestones bv ..hano. of tWv 1 ?W l^^"*7'";--'^«- ''^ ; ^^:^'>^' --^ P«-l-'"y subsequently, in 18^3. proposed to explain the genesis of the bedded petrosilcx-porphyries or halleflintas of Missouri by the transmuta- tion of a stratified lim.^stone. of which portions arc found interlaminated with the petiosilex. t II.>, at the same time, suggested a similar origin f,n- the hcmatitic iron-ore wnicJi accompanies thes(i porphyries. § 111. With this second hypothesis of the ori-iu of serpentines may be mentioned another, not, however, involving metasomatosis. which has sometimes been discussed and which was suggested by the present writer in 18;^, from the ivsults of ...rtain experiments on the artificial formation of silicates of lime and magnesia by the reaction between ..n- bonates oi th,>se bases and free silica in prcs.nce of heated solutions of alkaline carbonates, huch a reaction is not without its siguilicancc, and, as I have elsewhere shown, has doubt- less played a part in th.> local dcvlopincnt of protoxvd-silicates in sediments in the Vicinity of igneous rocks, and of thermal alkaline watej's ; but as an explanation of the gene- sis of great massesof comparatively pure silicates, su-'h as olivine, serpentine and steatite, it IS obviously inadequate, and was abandoned by the writer in 1800 for the view maintained below, t lilveii if we could suppose the presen.'c of .sedimentary b,>ds containing the requisite elements in proper proportions, it can be shown that the rea.'tions required for the production of silicates were inoperative in the very regions wh.'re serpentine and steatite are found, since side l)ysid.> with beds of these are to be met with in the Huroniau series, in many places, beds of dolomite and of magnesite intimately mixed with quartz, suJhcient in amount, if eombined, to .onvcri the ac.ompanying carbonates into <>orrcs- ponding silicates. § 112. There remain then to explain the origin of serpentine, besides the three hyiw- * ,^>i« for a .lis,MiHsi,m nf tl,,, view.s of tliiH srlmol tlio niitlior's CIum.i. and Giwl, Essayx, pj). 314-325 ; also, An Old ( haptor of till, Goologirul Uiuor.l, l.y KiiiK ami Kownoy, 1S81, chaptors vii. ami xii. t Zoological Survey of Missouri, Iron onw, otc, pj). av^T ; also tlio author on A/.oio Rovks, {)p, l-)4. t <'linirilcnl 1111(1 Goologioal liissuys, pp.25, 2!)7, 3(X). i 206 Di;. THOMAS STKUT^V IfFXT ON TIlM thesis jiist iioticiHl Ihivo others already mnitioiied. lo Avlii.h we niusi again refer. First of these, we have that whieh supposes the material of serpentine to have eome from the earth's intiu'ior as an iu'ne()ii.> fused mass consisting esseniially of olivine, whieh by snb- sequent hydration has l)een changed into serpentine. This stridiy plutonic hypothesis being, however, by many getdogists lield to be in<-ompatil>le with ol)served facts in the geognosy of serpentine, one whicli lias been called liydroplutonic and has already been set forth at length in these pativs, has found advocates. These, conceding that the geog- nostical relations of serpentine require us to admit thai it was laid down from water, have eonjeciured that a nntlerial so unlike that of ordinary a(pieous sediments was ej<'cted from the earth's interior, not in a stati; of igneous iluidity. l)ut as an aqueous magma or mud, consisting essentially of a hydrous silicate of magnesia, wliicii subsequently consolidated into serpentine, and even into olivine and ciistatite. This view, as we have seen, is main- tained by a s.hool of Italian geologists, and Daubree, whiK- holding to the oriu'in of ser- peidine by the hydration of a- plutonic olivine-roik. sui)poses this to have ]iassed into a hydrous condition before its ejtntion. * § 118. There are, however, no liiets in tin' history of vulcanism to justify this strange hypothesis of an erupt .'d mau'iiesian mud. The materials kiKuvii lo us as volcanic muds and ashes do not dill'er essentially, as regards their constituent chemieal elements, from other detrital matters, and the origin of this conjecture nniy perhaps be traced to the unfounded assumption that olivine is peculiarly a ]>lutonic mineral, and that rocks in which it and other magnesian silicates predniiiiuate are presumably jtlutonic in thtdr origin. liisatbest but a survival of the belief in a subterraneati i)rovidenc(>. whieh could send forth at i)leasure from its reservoirs alike uiaiiite and basalt, olivine-rock and linu'- stone, quartz-rock and mau'iietite. A rational science, however, .sei'ks lor tin' origin ol these A'arious and unlll:" mineral masses in the operation (if natural <'auses, and endeavors to exidain tlu'ir production in accordance with known >hemiral and physical laws. Knlightened geologists ari' now agreed us to the aqueous oriuin of limestones, of dolo- mites, of iron-oxvds and of quartx. by processes which are intelligible to every chemist, and the formation in the humid way of the native silicates of magnesia is e(]ually simple ami intelligible. v^ 114. It was, as already set forth in these pauvs, after a careful study of natural miiun'al-waters and sediments, and of the chmnistry of arlilieial magnesian silicates, that the l)resent writer, in IMIH, veiUured to assert the a(pU'ou.- firiuin of the nuisses of native nuignesian sili from (i.cayinu' rocks mid the maii'iic--iaii sails of iiaiiiral waters, t This view, although adojitcd by ntdes>e. as W" luuf shown in ^^ 11. and also, soon after by ( Jihnbi'l. by Crcdner. and by I'avre, | has not found ueiieral recognition. I have, how- ever, to record the recent adhesiou to it of Dieiilefait. the emiiH'iit cheiuisl and n'eoloLiist of Mar.seilles, whose arduous and oriuiiuil ^indies have already placed him in the n'oiit rank of .students in terrestrial clieuiistry : and also ol' Siaptf. ihc learned ami ai'ule uvolouist of the Si. (iotliard tunnel. * llreloiiiii F,X|l(^rinl('lltHll■, |i. 542. i- liiinl, 1 hnii. aihl Heel, lissays, pii. iL'J, LMir,, :il7. I llii>l. pp. :i(ii, ".(M, :;17. <-HOLO(ilCAL iUSTOIJY OF SKRPKNTIXKS, 207 ni'j. Tho conclusions of ])i,.,il,.r.,U .. i i tinos or Corsica, havo alvca.lv he,, ,a..nC k'!^;>" n""'""'-' '■'^"'"■^"" '^ '^'' «-!>-- ol tho ovisin of scrpcfi,..;, ib. (ho i;.l "''""' ^h. plutonic hvpothcsis -y thin hccis of sc,.c„ti,.c with l.!f iirrLr::: ^'j'" ""^'^^""^ '^'^^"'"'^'-^ «^ chansj. .n the constitution and co,„pos„ion o f 1 TI'' T ^'"">' ''""= ^^e 0-' Plare puro sorponiinc, hco,.,.. Jadu-,11 ' ,1 r'^!' 7'""; ^''-^-^ ^ ^heso, being- in 1-g.h ..onstitntcs a, h„,^c proportion othtl ^ ■ '■"■^""'"' ''^' ^•"^"- -'^^''^ ''* "-l^t of the cah.areous serpclti,,.,! To ^ 1 "'" ,^'* '"'"" '"^^""'"^' "^^-'^ '" ^^o of North Amori,.,, we n,ay add as no d . ,'' ' ' "''" '"""""^ *" ^'^" serpentines -dules, l.yers or lenticUa. ^ " "' ^ ' '^' "''r'"' I'"' '-^1"'-* '—nee of .rains, l>-ulef;,it notes, moreove,-, the d.Zn,. ;"'^"'""" '" ''^'^^^ "^ -•>-*'^"i»" Hmostone. I»«'t\vee„ the se,pentines and the'.n.d ,'l ""■ 7'"' "' '-""""' "'"'"'^ '^^ ^^o eontavt Plutonic hypothesis, and p.'vt n n I^ t -"'h^' "'^^ 1'' '"'' '^'""'^ '' ^'^^ ^^^'^- v^ no. His own con..l..;i. , " , "n ""'^"^ '""""'• the most con,pIete aeceptation of th ' , ' ■^"'i^'-'^^i'^'- ^'v ^edimentarv roeks in was not ,jected Iron. I W W t r^, , 1 • '"" "" ^^''"''"^ ^^^''■'^ -^ '■- *« ^J- tlu" silicious matters derivcnro^ t e 1 ' " ' """" ^' "" ^""^ ''>' ^-'■^^-^ between of the sea-water ; in which co^Z- ,t i , 1 r "'''''::' " '^ "^'^ ^'" "^'^^'^'-^ -!*« "^^^io,.s of the serpentines •. r ^''"" '^" '"^'"""^ metalliferous in.preo- I^i.'ulelairs, set lb,^h i 8 V w ;'r "'"^"^'' ^'-^"^ ^'- «'<^-' -^ks. This view of '-'t.d by Sterry Hunt,- t.^ni^'Z^Zi^7f:r ,'''':' '^"" " ^'" ^^^"^"^'^^^^^ '— himself on the ,p,cstion of the ,, , • '"' '"' '"'^ '''''' ''^^^^" •^•i" ^••■-•vin^ studies of t],os! of c!!rsl! . r : "■■•"7.^"^I"-''-^ of Italy, adds, alter his own ^vgard the phenonrena oliered bv tl s /""' '' ""^"'■^■^'^^'"- "■' ^Ji-'l^'f^'i' has said, to igneous or hyd.plutonic n I ,' . ZZ::! ^'V'^: '' '"' '' "'"^^'^""^ •'^''-- ^^ maintained by S.crrv Iluut C bv D , 7'"- .''^ '■'"';■■• '"- <^posi.ed as such, as --;t Weshal,no,,...,;arj;\::t^ -elvthehd':,^ .:'"•" 7-'-."'-ae and ens,a,ileorb,.onzite. an! n,ore and h, ,h,. o^Z-r^^ ' Z ' "'f '^''^ J'"'-"'- widely in densUy, in chen.ical stabilitv, one.;, i , h .U,^' :; • "^'i~-'>- ■' ^ •• -,- s,.,,>,.,„iue t : ,. These dille;: lions i„ . -''"^'^^':^ "* "^'' ^"i*^-"-'^ -"••u.n of se,-pe„„ue. may w.!! depe„,l upo„ varia- ti ^::7Tr '\ *"7^':""--"-"^ -'^^'>'^' ^"-"-. -^mpo,: .he lilance of " s b.tw .„ ., ,,, ,,„i ,,,,,„„„, ,,i,i, ., ,l,eu-a.ervme„struun,. „uher than upon ;!:^:':^::r,:;;::rt:'' :"';.-''^i'...;i-^a.e,oa.on,erbyadditio,.o,.:;;.r sen.enti.,.. i '"•'■:" ■^'''- ''« associat.o,,. „, ,1... sa.ne mass. „f a.>hv,lr„„s olivine with ..dm.ttmi. (he conver,snm. under certain ..onditions. of both ensia.ifo n.,7 .1,-.;...... J se o...-..>. ..o , ,.vu-u.ro, nie .nnagf ol oliv„ie mto .serpentim' • but versnm. under certain -•onditious.of both e„s(a(ite and oliviuo into * ,1,, i'A,.,„|. ,K,s .SM,.n.v,s xci. IdiiO 1.0..., .\H.ua.i U..,k^i..i .ulla CWm.u ; Mull. U. ,ouma.„ . iool,,,!.,, an.io ISSa. 208 I>T{. THOMAS STERRY HUNT ON THE hydiwis silicates, the view whi.li siipposes the olivine or the enstatite to he simply an instanooofthe.Tystallizationot'ananhydvous siUrato in the midst oi\.nani<.vphous hydrous silirale is more .'onsonant witli the hypothesis of the aqueous ori-in of serpentiiu-roeks. It is well known that Seheerer, irom his studies of the asso.iated olivine and serpentine of Snarum. was led to reject the notion of the derivation of this serpentine irom a pre- viously-lbrmed olivine, and to maintain a simultaneous formation of the anhydrous and the hydrous silicates.* A soniewh.t analogous case is presented in the or.urrcnce of ft-rains ol anhy- drous alumina or c^orundum found in the earthy and amorphous aluminous hydrate, bauxite, which forms beds iu uncrvstalline ceuozoic rocks, f The notion wiii.h has bc-en advanced that the ])auxiti> has come fnmi th.- hydration of previously-tormed beds ot rorundum is obviouslv untenable, and we must regard tlus anhydrous alumina as formed by crystallization in the midst of the unerystalline mass of hydrated alumina. De feenai- mont' in the decomposition of aciueous solutions of dilori.l of aluminum, at -250° L. observed a simultaneous produ.tion of anhydrous alumina in th. form oi corundum, and of hvdrous alumina as diaspor.", botli crystallized, t § no The late studies of Arno Eehr throw further light on the association ot hydrous and anhydrous species. He has found that solutions of dextrose, within very narrow limits of temperature and com-eutration, yi.-ld crystals either ot liydrated or anhydrous dextrose, and that under certain conditions we can .^])tain an admixture ol the two as the result of simultaneous crystalli/ation. v^ \ illustration of the inlluence of small variations in composition on the result ot a chemical process under conditions otherwise similar, is alloided by the recent experiments. of Friedel and Sarrasin on th.> artifi.'ial production of albite in the wet way. When a solu- tion of silicate of soda mixed with silicate of alumina in the proportions required to torm the soda-feldspar, was heated m close vessels to from m' to .100 C, no albite was iormed, but crystals of the hydrated doubl." silieate. analeinie: silica, soda, and scmie alumiia remainino- iu solution. When, however, an exc-ss of the alkaline silicate was employe , the whoh. of the silicate of alumina was converted into a erystallized anhydrous compound, whieh was albite. || • ,• r • • tr^ 4 110 Much obscurity still surrounus the ,,ue,stion of the .onversion oi olivine into serpentine. In the first place, it is to be remembered that the process is one which does uot un.ler ordinary circumstances, take pla.-e at or near the surface of the earth, simn^ olivine-rocks. whethi-r exotic inass.'s or i.idi-enous crystalline schists, are olten met with, pn'scntinu- no evidence of such .'hange. This is well seen near Montreal, where the hills of olivine-dolerite, d.'monstrably of pre-Silurian a-e, as well as IVa-ments ot the same rock imbedded in ^^ilurian •■onglomerates, alike- .ontain only unaltered anhydrous olivine This mim-ral, on expo.sed surfa.es. is subject to a subanial deeay. analogous to that * Sdiiwcr, Potrn. Aniuilni, Ixviii., :\]SK an.l .\iiiw, .T<,ur. S,i,.n.-e [-J] v. ;isu, vi,, L'ol, als- xvi., '.'IT. t IV.villo, An. (>, x.xxii., Tiil.'. \iiu>r. .Inur. Sci., lS(il \;2] xxxii., 2M, iih' . Vhvm. ami (icel. Rssay.«, y. liL'O. ?, For tli..M< farts I am in.U'l.tivl t.) i, private, cniniinmiralinn IVun, Dr. IVtir. S.v al>e, 1ms paiHT in Aniw. flii'iu. So(\, in ISSL'., vol. iv., \i. 11. II Otiiii.to.'j KouiUls do 1'Aca.l. ilos Scxnccs, .luly 30, ISSH. .Tour* Jf'MOia OF SEIJI'ENTINIX suffered by pyroxene and }inr«i.i , , ' "' ^09 ■""taul, wl.ilo, „t „,„ ,,,,„„ '": '='" »' ■n»gii.'sia. ,„„1 a,„„i,,. ,> '" «'' '"'"""t of 8ili,a, h.m=™- or paleo..i.. ao. , ";; ^^'".'''^ ^"-.^ 'be hi],, „, ,LnLvm ^^'"f ^'' o^iviae-dolerite tbe Utieashah::^ : ^;^ ^^ [^^ ^^''^-H.'", near I^I^^:^ ^^ ^L^'^^'^-f 7"^' — ""•"•■r«l in amber r , ' '""*"'""'^ ''^^'yAve n.r ,":, -^^ "^ ^'^'''^' alumiuous ' 1^2^~;"'''^"'^''"^ ^^•^of-.IirartjVr'''^' -^^>-h were 'Similar to the Z ^^'"''^^'"^"^ ^""-^ -*aIliue lime t ;e "if '■^ associated at Tbe ..rains o?l1^^ ^a-^'-uHan series elsewhere .^nd '"''"'" ^^^^^^^acbusetts. as Pjuu^f ^'""''^^^S-'-'-tweenthelinxestoneJhi^^^^^^^ * ««olw <.f fwT r " ' ^ ^'bondroduc and *="^'- «-«'«oGoo,o«K.al Report for lSOO,pago .05 i^^L'. IV., 188a 1.7. 210 Dli. THOMAS STKIJIIY ^U^'T oN THK sorpeiitino, unci those contaiiiing the puro magnosian olivinb, forstonto, aro very rloso, and thoir ivlations indi.'ato Ibr all cf Ih.nu a .ommon n^ptunian origin. « ]":] We pas8 irora tlu' oliviiu-boaving limo«tonos to those rooks composed .hiefly ol olivine, ^vhi.h have roeeived the names of dunite and Ihoizolite, and appear to be indi- genous interstratilied masses. Sueh was my eonclnsioii alter exanu.nng them m ^orth Carolina, in strata referred by me to the Montalba. s.ries, regarding whieh I ^vrote m 1879 • " Noticeable among the basic members of the terraiie is the granular olivine or chrysolite-ro.k which, often accompanied by eiistatite and by serpentine, appears to be interstratilied in the micaceous and homblendic schists of the Montalban m North Care- Una and in Georgia." * Olivine-rocks, similar to those of North rarolma have been observed among the crystalline schists in the provin.-e of Quebec, on the south side ot the Uulf of St. Lawrence, but have not yet been can-fully examined. ,„.,,, § l^i The typical Iherzolite from the eastern ryivnnees, described by Zirkel, has since been studied by lionney, who in 1877 t *3escribed the rock and its locality. It forms several masses of considerable size, near Vicdessos (Aricgc), and is in contact with a sac- charoidal limestone, in which occur broad tongue-like portions of the Iherzolite. Lhis rock consists of olivine with admixtures of enstatite, diopside aud picotite (a chromiferous spinel), the constituent minerals showing in their arrangement on weathered surfaces a "linear structiire," suggesting " an internal parallelism," whieh Bon.iey, who looks upon the rocks as " iinieous," regards as due to movements of How. The lock varies trom coarsely to finely granular in texture, and includes in some cases a serpent luic mineral m its joints. The dunite of New Zealand, in specimens before me. (.resents m the arrange- meut of the contained chromite, a well-deliiied gneissic structure. § 125. Similar rocks are found in NorNAay, specimens of which from ialiord, received by the writer in 1878 from Prof Kjerulf were mica.vous, and showed an evident y gneissoid structure. These rocks, consistintr essentially of olivine, holduig enst^ti^e, diopside, chromite and a greyish mica, are Iou-mI interstratilied in gm-iss. with quartzites and mica-schists, sometimes garnetiferous. From their late studies ol this rock in various Norwecrian localities. Toniebohm, Eeusch. and Br,-..rcr nuree that it must be classed amono- 'the crystalline schists, a judgment m which Kosenbusch .-oncurs. The reasons lor this conclusion, as set forth by Brogger. are briefly as follows : First, tlie invariably lam- inated structure of the olivine-rock. which is conlormable to that ot the enclosmg jvneiss • and, second, the variations in the composition of 'he rock itsdf as seen m adjacent lavers t With these -neissoid olivine-ro.ks of Norway may be compared the olivine known as glinkite. found i.i nodules in a talcose schist in the Urals, and also the schists Uu„ly descdhcd from Mount Ida in Greece. 5 In these, tlie transtt.ou is seen Irom true talc-schists to talc-schists containing more or less olivine, with pyroxene, and hnally to massive olivine-rock ; the whole being associated with other crystalline schists and with limestones. The obvious conclusion from all the above fact, is that no argument in favor ot the Igneous origin of serpentine can be drawn from its supposed derivation Irom olivine- rocks, since these are themselves, for the greater part, of neptumaiimagm^ * Mm farlane's Goolog'n'al lland-linok, page 13. t Goological Magazine, Fel). 1S77. J NOU...S .Tahrbiich fur :Miiierak«ie, ISSO, i., pp. 187, 10.5, 107. ^ Hcioiico, Aug. 31, 188a, p. 255. i GEOLOGirAT; lllfeTom' OF SHRPKNTINES. 211 I \ 111 thiH roiinottion may be noted the well-known fact of the aqueous deposition of Beri^entinein veins, in the forms of niavmolite, piciolite and ehrysotile, either alone or with calcite. Such veins, the result of a secondary process, are often found intersecting ophical- cites and serpentine ro-ks at various hori/.on.s. and are even met with in comparatively rei'ent serpcntine-hreccias, as noticed )»y Crastaldi (§ 42.) VII. — Stuatiobaphicatj Relations of Sekpentines. § 120. The coiitradictcny opinions expressed h\ dilForent observers as to the gooffuo^ il- eal relations of serpentine-rocks in a g-iven area — one regarding them as indigenous and another as exotic masses — make it evident that certain api»i'arances are dHferently inter- preted according to the theoretical ]ioint of view of the observer. In greatly crusii'Ml and displaced strata Die varying resistance of unlike roiks undoubtedly gives rise to accidents which are regarded by many as evidences of posterior intrusions. The serpentines and related rocks of Carrick in Ayrshire, Scotland, may be cited as another instance of this conflict of opinion. As descrilx'd by .Tames Geikie in 1800,* the serpentine and its associated greenstones are both indigeiion.' ■• Ided rocks iuterstrati- lied with greenish crystalline schists which he, following Murchisou, called altered Lower Silurian. Creikie, however, found what he regarded as clear evidence that these strata had been greatly disturbed while in a soft«'ned condition. The remarkable resemblance between these crystalline schists of Carrrick and those associated with the serpentines of Cornwall, is noticed ])y "Warrington Smyth. Bouncy, in 1878, f rejected the conclusions of Geikie, asserting that we have in Carrick, as elsewhere, truly eruptive serpentines, followed by eruptive gabbros of two ages, and like Geikie, addueeed evidence in support of his own views. § 127. In a critical notice, in 1878, of Trof. Bonney's description of the serpentines of Cornwall and of Ayrshire, tlie present writer said : " When it is consid.n-ed that there is abundant evidence that the North- American serpentines are indigenous, though often, like deposits of gypsum and of iron-ores, in lenticular masses ; and further, that thi" movements which the ancient strata have suH'ered, have produciMl great crushings aiul displacements, it is not dillicult to understand the deceptive appearance of intrusion which these rocks often exhibit, and which are scarcely more rt'markable than the accident':- presented by coal-seams in some disturbed and contorted areas." % Tlie alternately thickened and attenuated condition of coal-seams in such districts, and the forcing of the coal into rifts and openings in the enclosing sandstone-strata, is familiar to those who have studied the I'ontortcd measures of the Appalachian coal-field. The latter phenomenon especially is well displayed in one of the elaborate sections made since 1878 by Mr. Charles A. Ashburuer, and just published by the geological survey of rennsylvania, in which the so-<'alled Maminoth-vein is shown as it occurs in the Green- wood basin of the rantlier-Creek district. § The accidents in this great forty-foot y.>am of anthracit(>, here represented on a scale of one inch to 400 feet, are such as would, in a rock of conjectured igneous origin, be deemed strong evidence of its intrusive character. * tiw.l. Journal, xx., .">L'7. t H'''^. xxxiv., 7S!i. X Ilarjwr's Annual Ki'mnl, 1S7S, p. LMi;5. ? Stioind (iodl. Sui-vcy nf I'ciiii., vol. I., Sniithcni Cdul-Fii'ld ; Cms.s-Siictinii Sluidt ii., Softion 10. 212 PR. THOMAS STHItPvY HUNT ON TIIK § 108 Wc have already referred to the coudusions of Stapff with regard to the indigenous character and sedimentary origin of serpentines. The obsei^-ations of ilns eminent engineer and geok^gist, while superintcndin.r the work of the tnnne through Mol" St. G ^t.ard, from (lo'chenen to Aiv.k. in the years 1S7B-1«80. are set lorth a kno-th in nis recent memoir ac.ompanyi.ig a geok.gieal section, * whi-h we have notn-ed in ? r>Y. Lenticular masses of serpentine appear to the east and west of the tumuli, a ong the line of which they are intersected between 4,8t0 and 5.310 meters from he northern terminus. Having descril,ed at length the rocks of the section, he adds : >\ e have ni .vhat precedes saM nothing of th.- stru..turc of the sevpentine, noi^ ^-^J ^^'^^'T' ^ potrooraphic point of view, it is to he separated IVom th. other rocks ot he St. Gothard lu ,asA,ecise it evidently .u.s th.e last, so that it might be .ons.dered as a rock intruded axaong them." Havingstated in detail its vckt ions, he ..Us us that "the ],oundarn.s of the serpentine-mass sometimes IhUow the stratilieation ol the neighboring rocks, mt sometimes go across it." Yet. he liasteiis to add, "we nowhere iind plausible proo of the penetralion of the serpen. uie-n.ass into ,hc cieasing voeks. This serp.M,ti,ie had orio^inallv the lovm of a Ihdtened lenti. ular mass, inteivalatcd eonformahly lu the strntih- catLi (in.e the layers of eulysite in the gneiss nf Tunabertr. in Sweden), and now appears, us the result of numerous breaks and displacements, out.Topping in a series o. h|tle k^ses, the line ioining which intersects at a sharp angle the sehistose lammatum oi the beds. t^l he ii^ures whieh, with displaeenien.s. eul '^^ '-- ^|^V''" .'''"'T TL h^ Lpeutino is stretched out and pushed back (.//... c/ njo.la:) h-.h at the surlac and m the "'^' n'21^ ™!'displacement in one cas. , on the surf-ice, was lound equal to 4o() motors, and the adja..ent strata were bent in the lonn of an inveitcd C. The maximum thi,-kne^ of the serpentine at the outen.p was 100 meters, and the thickness ot 440 metes, ^ hi. 1 it attains in the line of the tunnel, is believed by the author tobeduetothe ac..uuulati..n, bv the movements deseribed, of suceessive portions of one and the same lentu^ilar mass : a emiclusion which is illustrated by a great number of minute „l>ser^ at ions. He adds, the iissures along whidi this heaping-together mu.l have taken place, pn.ent stnations pu- ;incedbv,h:sliding..f the , k; they arc c.ated with a --'^tic matte, and sonidm^^^^ imedwitha IVietion-bicccia. KaitluT prools of this crushing are lound '-t'--^' diseon.inuity of the sehisf.se and compact portions of the serpentine, and m the m.knh outline presented by the upper suriace ,.f the serpentine-mass . a detail no -presented n the proille." The autk.r farther says :-" Although we woul.l no consider he se,,., n- 1- ie\,. be an intrusive rock, we must remark that i, coidd imt have had precisely the same l,.e,.hanieall sedimentary origin as that which we have supposed lor the micaceous gneiss ;,„..,, .,,.lLes it. AVe may rcard it as originally a deposit ol hydra.ed sdici.e ma.nesia. Ibrn.e,! l.y springs, and enel.sed bCw.-en lie sc.limenis wlueh .avc nse to miea-schists." The hvdrated n.a.nesian sili.ate is supposed by our author to liN c bui subsequent ivonvertJd into anhydrous olivine, etc whieh by a aler ^'''^^ll ^ ..vneraled se"rpei,tine. pnrtiuns of ..iivine still reiiiaininu' m the mass, h may be qu.«stiom d Whether the phenomemt require this hypothesis of a 'l"uble ehang.^ lor their explana- , ;,,„i.l Tuniirl, -in- iino 1: '.'■'."(Ul, im-r toxt exi.liriilii; piir I'f. V ^K rit * IVoIll p'.il(«i()Ui' ilii St. (loliiur.l iliin: ]■. M. Slii|iH'. I . I'p. <'''\ llenio, IhHl, iixo ilu GEOLOGICAL HISTOEY OP SERPENTINES. 213 ftii tioii. The serpeutlne coutaius imbedded, in some portions, not only olivine, but horn- blende, talc and garnet. Intercalated with the serpentine, which is often distinctly stra- tified, Ire layers of schistose talc, of compact chlorite, of actinolite-rock, of ferriferous dolo- mite, and of mica-schist. The serpentine itself is chromiferous, and also contains magnetite. \ 130. Dr. Htaplf farther adds :— "The curious modifications of form which the mass ^of serpentine has suffered from the elll'ct of faults, etc., correspond to those of the adjacent micaceous gneiss, but in thi! case of the former they have been better studied, for the reason that it is mOTe easy to define the limits of these forms. If we suppose, in the section, in place of the serpentine, a mass of ordinary micaceous gneiss subjected to all the movements of' displacement and elevation which we have here displayed, we should perceive nothing more upon the profile than a uniform surface of micaceous gneiss, with some mter- lacing8"'of beds. It cannot, however, l>e denied that movements arr.^sted by the hard and tough mass of the serpentine have produced in th(> neighboring rocks perturbations much moi^e intense than would have resulted from similar movements acting upon a more tender rock " (1..C. cit., pp 4:1-44.) It woiild bi' difn.ult to illustrate more .'learly than Dr. btapfi has done, the maniuT in which movements in th<' earth's crust may effect interstratified masses of unequal hardness and tenacity, giving rise io accidents which simulate to a certain extent those produced by the intrusion of foreign masses and may thus lead dit- fc-rent observors, as we have .seen, to opposite .-onclusions with regard to the geognosticai relations of rocks like serpentine and euphotide. VIII.— Conclusions. The followring are the chief points regarding serpentine and ophiolitic rocks which wo have sought to set forth in the preceding pages :— 1 To show histori.'ally the diversity of opinions as to the geognosticai relations ot seri>eutine and related rocks, which hav been rcuarded by some writers as eruptive and of igneous oriuiii, andi)y others as aqueous and sedimentary. ^ 2 To show how, from th.> hvpothesis of their .'ruptive ..rigin, .'ame the application ot that of metasomatosis, and also to set forth the hypothesis of the aqueous origin ot serpen- tine, explaining how silicates of magii.>sia may, «n chemical gnnuuls, be looked tor at any geological horizon. , . xr n a ;i To indicate the various horizons at \vhich serpentines arc fouiul in North America ; and first, thos,- of the Laureiitian, of th" lluronian, and of the y.mnger or Montall.an gneisses ; in which connection we have noticed the serpentines of Chester county, leim- .ylvania, and those of New liochelle, Ilobokcn, and Manhattan and Stalen Islands, all ol which are regarded as in.li-enous stratiiicd rocks; the apparently intrusive character ol the serpentine of the latter locality Ix'ing explained. , n. • 1 4 We have further d.'scrihed the ...cunvncc of serpentine ann.n- thelacmiaii rocks in rcnnsvlvan.a, and also anions the ^ypsilerous rocks of the Silurian series at Syracuse, onieiiclaturc of serpt'iitine and related New York. 5 ILiving noticed .some points regardinu' the no ro..ks.and B.>nnev-s a .unl .>f the serpentines of Cormvall. and of ^^^^^ f ^y^ ^'^;^'' considered the serpentine-bearing ro<.ks of the Alps, in which we show iouV u.-eat gioups, Hscendin- or.ler, which are tlic older uneiss, the pietre-verdi or greensloiie-senes, tho in 2J4 ■ ™ THOMAS STEETIY IITJKT ON TIIE 0^ tholy to tW L>„m.nli„„, H«ro„ia„, Montalban and TMOnum o. North Amor.a , tte „„d and third of th.^- l.ei,,s Iho r.bidi.n and tho Ovamp.a,, ol <>'-'' r'"';" ; * J lth,os,it.-a, »ho>vn,o.u,. in tho Alps int..r.t,a,iii... in th« ..vond. ihnd and lonUh of thes,. "-roiips, tho voWKVst of which in.lnd™ Iho inariJos ol (.,arrara. Tl °v V tha't this vonngost gvonpin mosozoio, isdisonssod, and tho volat.ons o al the.o "roups of orystallino sohists to th» fossililorons rooks of tho man.land and ol Ihoso o El f^>Xdini, aro sot forth, showing thoir pro-Camhrian ago ; w^hdo .t ,s man, an,M !;'rt tin. ophiolitos and othor orystallino rooks whioh havo thovo hoon rolorred to tho tortiary aro Imt oxposod portions of thos,. pro-C»mhrian roota. ,/Tho orvstaUino rooks of tho Simplon and tho S,. (io.hard, and thoso o ft .ony .""1 Bavnia aro oinsidovod and aro oomparod with tho yonngor gno.ssos ol North Am, r oa 8 Tho . lations of tho s„..-allod tortiary sovpontinos to iho surronndmg strata aro .dnol^l l,v : d'Liloa disonssion of tho „n.ss of Montolorralo, in Tnsoany, whn-h .s '^^t"Thr;:ri:rr::i::',™:=;:f:.piain tho gonosi, ot sorpommos ^o oons,dorod. ""^r'^o"::z3 >:::;o:;;?t:;;;t is disonssod d ...o ossomiauy nopinman "'^'";'rr™d;:::;™':''::tr goog,,„s.ioal ..atlons of .rpontmo arooonsl. dorod a,! . tnpt is nrado to show that Iho ap. a, »;';;"'"-;>;■.;;';- "''l^ some havo ins>s,od. aro o.plainod l,y .nl,so,,„ont movomonts ol Iho strata m whnh the serpoutiuos aro iinhidocl. CoMKNTS OF Sections. rn,.ksin,^.miral;10.8upi,oso.luu4asoniatuw,n,uw.fsoriK.,nt.nos,ll-l^^^^^^ i ,,oat pr.iUlom ,sor,xM.tin... an.l of ori.ptivo rofkn ; i;!-14. Aquooiis ft.rniation ot niaK.u.b.an mIp atcs , 1... A , t 1 in cluMiiifal f-'foloi-'V. ::;;r::S;;t; ta!;,T::r:^; ■.r"::;::;;,:;; ..,:. s.,™,, . s.™,„o, .,. v,,. ..w..„„„„ antl'a.u.lylis ; :V.. Sopiolito and otlior maiincsian siliratf. a mpiun ni,' ^'vpsni... . ',-,•.„ > ■Ni-'!H liniuiov on tho s..v,K.iiti.u. of Cnnivvall ; I'.'.Mli. Tho nan.oH of opliiolito ^"•^'''s:;;:::::i,;hZ::;:; tL/noi.,.^ u.l .; .m. .^rpo^ahu. at tuo «oo.i...ai ■"M;ro„.ah.tohos i'''U.e;t..Ano,ila,ist.n,.,.hi;.i.os..,,.ian,n^ ,.tro.ilox.r,i,.k., passin, into ,„uu.Uilo,.ou. p.irphyra.. an,l i. irH "'",;, ,,„„ ,,„ ,„r,,„.inoH, ,H«ofNonhAmori..a,ana.,fOn.atliniain,.«no.ropn.t<.o 1.1 A ^^^ ,,f,.)upti\o. nifsi./...H'iiiia.vnn/.,,if iiia^Hi.s, ami .snmv, i " , ,,' „ ,, „ ,„,„,.,/il,M-nus iiorplivrios which aro ho '"-'>■ ■'■■"''"•:'\"V!;':r;,";.t:;::;:rHt^ :„,,,,.,,,.,,.u.i..,^.„ .u»,t, .», T »« (f^^PW^VJ-tW GEOLOGICAL HISTORY OF SERPENTINES. 218 f'f congress of Bologna ; 4(5-17. Tlio .listiuction <.f ooi-x)!. and conozoic sori«ntino« iii Italy ; their geographi- cal distribution. iy.-G,oloo>j of a. Alps ana Apennines.-, 4S. Thcori^ a« to Alpine ^^^f^^ l^,:^:^:lJ:!r^l 50. Sections by Kori and by Gerlach, in the M estcrn Alps; .l-o.>. Seet.on. ^^l''^^'^ .^ \ ..ietre-verdi newer gneiss, youngest schists ; 5:5. Chara.-tors of newer gneiss; o4. bection in to Br, k.so , ^ T^ p e^ ^t.li zone i.r its wider and its narrower .eiise; 58. The youngest -^y^^f^ 1^;e^;dcUness of these Alpine roeUs ; .0. Von llauer's sections in the Eastern Alps ^^'^^^ Siniplon- Primitive schists of Lory ; 6'.Mi(5. The lustrous schists; (i,. Kocks of tlie St. Gothard «. C i'and s.w.alled porphyries ; nO. (.'lassiiication of Alpine crystalline rocks in four|« -^ The. i tions tof.>ssiliferous strata; 71-7;-,. deoln.y of Corsica an.l Elba; 74- Zoology of bardina;.t_s C^n- Si^ Lna ; Ordovican [..ot-note] ; 75. Change of views as to the age of cry stalhne ^^;^ Lirbles of Carrara; 78. Studies in the Valtelline; 711. The granuhtic series of Saxony ; SO. Conglomerates li::Z^:^ g-Usses; primitive Hay-slate series ; 85-80. t^astaldi on the continuity ot the A,, and AiHinninos, and the geognosy of sori)entines. 107. Tlie Staten Island serixuitino. • . c- ,in „ 3 108 r«l l»v metasomatosis of plutonic masses ; conversion of feldspathic rocks VI._r/„. aene.s ,f f '^j f j;" , " j,^^ ;, .^ ^ limestone; of serpentine to limestone; King and Kow.iey ; ,0 serix.n me; 10... ''„,..^„ ,„„,,,,. ,„pi,.,sed change of limestones to sen.M.tine ; to granite, 110. r'^l By mutusomatosisol lupiunuin Ilia. M. , ii ,. t iioir! Ml Rv ilteration 1 ,. ;i>v.in M Hvdia"enesisnf silico-magnesian se(bnients; 11J-11-. L''! ^.^ 'I't'-r'"'"" ,-,',,, ,„i Hi,.,, , Ll »„,l I.,.lli ». 11» »>.li»»»t«'y orivii. ,.f <■•■",..».. .or,»»t,i.i..; 1 .-!.'. ton- s::::s::"i™"™,=::-:""" " "-™- -- ' "•'"- "-" '■""- genous duiructer; .ilivine-beariug s.'liists. ,• ,,.;/; „. „r <^,r,>enlinrs-i l-'O. Contradictory opinions; (ieikie and llonney on Ayrslure yU.-S!r.,nn,■ in (Mobor 1883, tho tmthor has rcrcried to results Lotli, (5 12, M) and tho oxperimouls noted m Slln.-ll. s. ll.| »l«